View Filing Data

Print Document View Excel Document

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	WLK
Entity Registrant Name	WESTLAKE CHEMICAL CORP
Entity Central Index Key	0001262823
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		129,165,391

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 788	$ 1,531
Accounts receivable, net	1,241	1,001
Inventories	939	900
Prepaid expenses and other current assets	36	31
Total current assets	3,004	3,463
Property, plant and equipment, net	6,519	6,412
Goodwill	1,008	1,012
Customer relationships, net	550	616
Other intangible assets, net	141	161
Other assets, net	499	412
Total assets	11,721	12,076
Current liabilities
Accounts payable	626	600
Accrued liabilities	675	657
Current portion of long-term debt, net	0	710
Total current liabilities	1,301	1,967
Long-term debt, net	2,667	3,127
Deferred income taxes	1,184	1,111
Pension and other post-retirement benefits	303	344
Other liabilities	178	158
Total liabilities	5,633	6,707
Stockholders' equity
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.01 par value, 300,000,000 shares authorized; 134,651,380 and 134,651,380 shares issued at September 30, 2018 and December 31, 2017, respectively	1	1
Common stock, held in treasury, at cost; 5,486,164 and 5,232,875 shares at September 30, 2018 and December 31, 2017, respectively	(337)	(302)
Additional Paid in Capital	562	555
Retained earnings	5,400	4,613
Accumulated other comprehensive income (loss)	(24)	7
Total Westlake Chemical Corporation stockholders' equity	5,602	4,874
Noncontrolling interests	486	495
Total equity	6,088	5,369
Total liabilities and equity	$ 11,721	$ 12,076

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, par value, in dollars per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, in dollars per share	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common Stock [Member]
Common Stock, Shares, Issued	134,651,380	134,651,380
Common Stock, Held in Treasury [Member]
Treasury Stock, Shares	5,486,164	5,232,875

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 2,255	$ 2,109	$ 6,640	$ 6,031
Cost of sales	1,716	1,613	5,007	4,766
Gross profit	539	496	1,633	1,265
Selling, general and administrative expenses	114	98	337	298
Amortization of Intangibles	24	27	75	82
Transaction and integration-related costs	5	7	20	23
Income (loss) from operations	396	364	1,201	862
Other income (expense)
Interest expense	(28)	(40)	(96)	(119)
Other income, net	23	4	53	13
Income before income taxes	391	328	1,158	756
Provision for income taxes	73	109	255	233
Net income	318	219	903	523
Net income attributable to noncontrolling interests	10	8	30	21
Net income attributable to Westlake Chemical Corporation	$ 308	$ 211	$ 873	$ 502
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (usd per share)	$ 2.36	$ 1.62	$ 6.70	$ 3.87
Diluted (usd per share)	$ 2.35	$ 1.61	$ 6.67	$ 3.85
Weighted average common shares outstanding:
Basic (in shares)	129,427,328	129,069,186	129,512,097	129,033,597
Diluted (in shares)	130,052,292	129,888,968	130,183,201	129,789,965

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 318	$ 219	$ 903	$ 523
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect [Abstract]
Pension and other post-retirement benefits reserves adjustment	12	1	12	2
Income tax provision on pension and other post-retirement benefits liability	(3)	(1)	(3)	(1)
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	0	40	(43)	111
Income tax benefit (provision) on foreign currency translation	0	0	1	(2)
Other comprehensive income (loss)	9	40	(33)	110
Comprehensive income	327	259	870	633
Comprehensive income attributable to noncontrolling interests, net of tax of $1 for the three months ended September 30, 2018 and 2017; and net of tax of $3 and $2 for the nine months ended September 30, 2018 and 2017, respectively.	10	8	28	23
Comprehensive income attributable to Westlake Chemical Corporation	$ 317	$ 251	$ 842	$ 610

Consolidated Statements of Comprehensive Income (Unaudited) OCI Parenthetical - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
OCI Parenthetical [Abstract]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	$ 1	$ 1	$ 3	$ 2

Consolidated Statements Of Changes In Stockholders' Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Common Stock, Held in Treasury [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Beginning balances at Dec. 31, 2016	$ 3,892	$ 1	$ (319)	$ 551	$ 3,412	$ (121)	$ 368
Beginning balance, shares issued at Dec. 31, 2016		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2016			5,726,377
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	523				502		21
Other comprehensive loss	110					108	2
Shares issued—stock- based compensation (in shares)			(174,684)
Shares issued—stock- based compensation	2		$ 4	(2)
Stock-based compensation	10			10
Dividends declared	(76)				(76)
Distributions to noncontrolling interests	(21)						(21)
Issuance of Westlake Chemical Partners LP common units	111						111
Ending balances at Sep. 30, 2017	4,551	$ 1	$ (315)	559	3,838	(13)	481
Ending balance, shares issued at Sep. 30, 2017		134,651,380
Ending balance, Treasury shares at Sep. 30, 2017			5,551,693
Beginning balances at Dec. 31, 2017	5,369	$ 1	$ (302)	555	4,613	7	495
Beginning balance, shares issued at Dec. 31, 2017		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2017			5,232,875
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	903				873		30
Other comprehensive loss	(33)					(31)	(2)
Common stock repurchased shares			515,853
Common Stock repurchased	(49)		$ (49)
Shares issued—stock- based compensation (in shares)			(262,564)
Shares issued—stock- based compensation	8		$ 14	(6)
Stock-based compensation	13			13
Dividends declared	(87)				(87)
Distributions to noncontrolling interests	(37)						(37)
Ending balances at Sep. 30, 2018	6,088	$ 1	$ (337)	$ 562	5,400	$ (24)	$ 486
Ending balance, shares issued at Sep. 30, 2018		134,651,380
Ending balance, Treasury shares at Sep. 30, 2018			5,486,164
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 1				$ 1

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income	$ 903	$ 523
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	473	449
Stock-based compensation expense	16	17
Loss from disposition of property, plant and equipment	26	14
Deferred income taxes	74	23
Other gains, net	(20)	(3)
Changes in operating assets and liabilities
Accounts receivable	(252)	(185)
Inventories	(42)	24
Prepaid expenses and other current assets	(3)	17
Accounts payable	36	61
Accrued liabilities	9	57
Other, net	(65)	(35)
Net cash provided by operating activities	1,155	962
Cash flows from investing activities
Additions to property, plant and equipment	(507)	(414)
Additions to investments in unconsolidated subsidiaries	(63)	(47)
Other, net	9	1
Net cash used for investing activities	(561)	(460)
Cash flows from financing activities
Dividends paid	(87)	(76)
Distributions to noncontrolling interests	(37)	(21)
Proceeds from notes payable and drawdown of revolver	11	231
Net proceeds from issuance of Westlake Chemical Partners LP common units	0	111
Repayment of term loan	0	(150)
Repayment of revolver	0	(550)
Redemption and repayment of notes payable	(1,177)	(7)
Repurchase of common stock for treasury	(49)
Other	8	2
Net cash used for financing activities	(1,331)	(460)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(6)	22
Net increase (decrease) in cash, cash equivalents and restricted cash	(743)	64
Cash, cash equivalents and restricted cash at beginning of period	1,554	646
Cash, cash equivalents and restricted cash at end of period	$ 811	$ 710

Basis of Financial Statements	9 Months Ended
Basis of Financial Statements	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Financial Statements	Basis of Financial Statements The accompanying unaudited consolidated interim financial statements were prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim periods. Accordingly, certain information and footnotes required for complete financial statements under generally accepted accounting principles in the United States ("U.S. GAAP") have not been included. These interim consolidated financial statements should be read in conjunction with the December 31, 2017 consolidated financial statements and notes thereto of Westlake Chemical Corporation (the "Company") included in the annual report on Form 10-K for the fiscal year ended December 31, 2017 (the "2017 Form 10-K"), filed with the SEC on February 21, 2018. These consolidated financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Company for the fiscal year ended December 31, 2017 with the exception of those accounting standards adopted in 2018 as discussed in Note 1. In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of September 30, 2018, its results of operations for the three and nine months ended September 30, 2018 and 2017 and the changes in its cash position for the nine months ended September 30, 2018 and 2017. Results of operations and changes in cash position for the interim periods presented are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2018 or any other interim period. The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Certain reclassifications have been made to the prior-year financial statements to conform to the current-year presentation. Recent Accounting Pronouncements Leases (ASU No. 2016-02) In February 2016, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The standard requires adoption using a modified retrospective approach and allows for the election of certain transition practical expedients. The accounting standards update allows for certain transition expedients for leases that commenced prior to the adoption of the new standard. Under the optional transition expedients an entity is not required to reassess (1) whether any expired or existing lease contracts are or contain leases, (2) the classification of leases as operating or capital leases or (3) whether any initial direct costs qualify for capitalization under the new accounting standard. These expedients are required to be elected as a group. The accounting standards update also allows the use of hindsight to determine lease term when considering lease renewal or termination options. During 2018, the FASB issued additional authoritative guidance that provides an optional transition method which allows entities to continue applying the existing lease guidance in the comparative periods and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The FASB also issued an accounting standards update that allows entities to apply their existing policy for accounting for land easements that exist as of, or expired before, the effective date of the new lease standard. The Company is in the process of evaluating the transition method and other expedients it may elect. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Company is in the process of reviewing its existing lease agreements and evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Income Statement - Reporting Comprehensive Income (ASU 2018-02) In February 2018, the FASB issued an accounting standards update to (1) allow reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the U.S. Tax Cuts and Jobs Act (the "Tax Act"); and (2) require certain disclosures about stranded tax effects. The accounting standard will be effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Company is in the process of evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Fair Value Measurement (ASU No. 2018-13) In August 2018, the FASB issued an accounting standards update to modify the disclosure requirements on fair value measurements. The amendments are effective beginning after December 15, 2019. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until the effective date. Most amendments should be applied retrospectively, but certain amendments will be applied prospectively. The Company is in the process of assessing the impact of the standard on the Company's fair value disclosures. However, the standard is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2018-15) In August 2018, the FASB issued an accounting standards update to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). The amendments are effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The amendments should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company adopted the standard on October 1, 2018, prospectively, and did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standards Revenue from Contracts with Customers (ASU No. 2014-09) In May 2014, the FASB issued an accounting standards update on a comprehensive new revenue recognition standard that supersedes virtually all previously issued revenue recognition guidance. The new accounting guidance creates a framework by which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities are required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for "modified retrospective" adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers ("ASC 606"), effective January 1, 2018. The Company applied the modified retrospective transition method to all contracts that were not completed as of the adoption date. Periods prior to January 1, 2018 were not adjusted and are reported under the accounting standards that were in place during those periods. The cumulative effects of changes to the Company's consolidated January 1, 2018 balance sheet for the adoption of this accounting standard were immaterial. The impact of ASC 606 adoption on the financial statements for the three and nine months ended September 30, 2017 as compared with the guidance that was in effect prior to January 1, 2018 was immaterial. Revenue is recognized when the Company transfers control of inventories to its customers. Amounts recognized as revenues reflect the consideration to which the Company expects to be entitled in exchange for those inventories. Provisions for discounts, rebates and returns are incorporated in the estimate of variable consideration and reflected as reduction to revenue in the same period as the related sales. Control of inventories generally transfers upon shipment for domestic sales. The Company excludes taxes collected on behalf of customers from the estimated contract price. For export contracts, the point at which control passes to the customer varies depending on the terms specified in the customer contract. The Company generally invoices customers and recognizes revenue and accounts receivable upon transferring control of inventories. In limited circumstances, the Company transfers control of inventories shortly before it has an unconditional right to receive consideration, resulting in recognition of contract assets. The Company also receives advance payments from certain customers, resulting in recognition of contract liabilities. Contract assets and liabilities are generally settled within the period and are not material to the consolidated balance sheets. The Company expenses sales commissions when incurred. These costs are recorded within selling, general and administrative expenses. The Company does not disclose the value of unsatisfied performance obligations because its contracts with customers (i) have an original expected duration of one year or less or (ii) have only variable consideration that is calculated based on market prices at specified dates and is allocated to wholly unsatisfied performance obligations. ASC 606 requires disclosure of disaggregated revenue into categories that depict the nature of how the Company's revenue and cash flows are affected by economic factors. The Company discloses revenues by product and segment in Note 14 to this quarterly report on Form 10-Q. Recognition and Measurement of Financial Assets and Financial Liabilities (ASU No. 2016-01) In January 2016, the FASB issued an accounting standards update making certain changes principally to the current guidance for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. Among other things, the guidance (1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value, with changes in fair value recognized in net income; (2) allows entities to elect to measure equity investments without readily determinable fair values at cost, less impairment, adjusted for subsequent observable price changes (changes in the basis of these equity investments to be reported in net income); (3) requires an entity that has elected the fair value option for financial liabilities to recognize changes in fair value due to instrument-specific credit risk separately in other comprehensive income; (4) clarified current guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities; and (5) requires specific disclosure pertaining to financial assets and financial liabilities in the financial statements. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. The Company is party to a joint venture investment with Lotte Chemical USA Corporation to build an ethylene facility, LACC, LLC ("LACC"). The Company measures its investment in LACC at cost, adjusted for observable price changes because the investment does not have a readily determinable fair value. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-18) In November 2016, the FASB issued an accounting standards update to clarify certain existing principles in Accounting Standards Codification 230, Cash flows, including providing additional guidance related to transfers between cash and restricted cash and how entities present, in their statement of cash flows, the cash receipts and cash payments that directly affect the restricted cash accounts. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018. Upon adoption, the Company retrospectively adjusted its financial statements to reflect restricted cash in the beginning and ending cash and restricted cash balances within the statements of cash flows. As a result of this retrospective adoption and reclassification of restricted cash and cash equivalents, net cash provided by (used for) financing activities on the consolidated statement of cash flows for the nine months ended September 30, 2017 has been adjusted to $(460) from the originally reported $(306) to reflect the retrospective application of the new accounting guidance. Previously reported cash and cash equivalents at beginning of the period and cash and cash equivalents at end of the period for the nine months ended September 30, 2017 have been adjusted to include restricted cash of $186 and $32, respectively. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in ASC 606. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted the accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income—gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Retirement Benefits (ASU No. 2017-07) In March 2017, the FASB issued an accounting standards update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires employers to disaggregate the service cost component from the other components of net periodic benefit cost and report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The amendments also allow only the service cost component to be eligible for capitalization when applicable. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Stock Compensation (ASU No. 2017-09) In May 2017, the FASB issued an accounting standards update to provide clarity and reduce both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require the application of modification accounting in Topic 718. Essentially, an entity will not have to account for the effects of a modification if: (1) the fair value of the modified award is the same immediately before and after the modification; (2) the vesting conditions of the modified award are the same immediately before and after the modification; and (3) the classification of the modified award as either an equity instrument or liability instrument is the same immediately before and after the modification. This update is to be applied prospectively to an award modified on or after the adoption date. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities (ASU No. 2017-12) In August 2017, the FASB issued an accounting standards update to improve financial reporting of hedging relationships, to better portray the economic results of an entity's risk management activities in the financial statements and to simplify application of hedge accounting guidance. The accounting standard eliminates certain hedge effectiveness measurement and reporting requirements and expands the types of permissible hedging strategies. The accounting standard will be effective for reporting periods beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance, to be applied retrospectively to the beginning of the fiscal year. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows.

Financial Instruments	9 Months Ended
Financial Instruments	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments Cash Equivalents The Company had $355 and $644 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at September 30, 2018 and December 31, 2017, respectively. The Company's investments in held-to-maturity securities were held at amortized cost, which approximates fair value. Restricted Cash and Cash Equivalents The Company had restricted cash and cash equivalents of $23 at September 30, 2018 and December 31, 2017. The Company's restricted cash and cash equivalents are related to balances that are restricted for payment of distributions to certain of the Company's current and former employees and are reflected primarily in other assets, net in the consolidated balance sheets.

Accounts Receivable

9 Months Ended

Sep. 30, 2018

Accounts Receivable, Net [Abstract]

Accounts Receivable

Accounts receivable consist of the following:



	September 30, 2018			December 31, 2017
Trade customers	$	1,171		$	974
Affiliates	11			9
Allowance for doubtful accounts	(24		)	(22		)
	1,158			961
Federal and state taxes	55			7
Other	28			33
Accounts receivable, net	$	1,241		$	1,001

- Definition

The entire disclosure for claims held for amounts due a entity, excluding financing receivables. Examples include, but are not limited to, trade accounts receivables, notes receivables, loans receivables. Includes disclosure for allowance for credit losses.

+ References + Details

Inventories

9 Months Ended

Sep. 30, 2018

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	September 30, 2018		December 31, 2017
Finished products	$	566	$	549
Feedstock, additives, chemicals and other raw materials	221		221
Materials and supplies	152		130
Inventories	$	939	$	900

Goodwill (Notes)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill Disclosure [Text Block]

Goodwill

The gross carrying amounts and changes in the carrying amount of goodwill for the nine months ended September 30, 2018 were as follows:



	Olefins Segment		Vinyls Segment			Total
Balances at December 31, 2017	$	30	$	982		$	1,012
Effects of changes in foreign exchange rates	—		(4		)	(4		)
Balances at September 30, 2018	$	30	$	978		$	1,008

The Company performed its annual impairment analysis for the Vinyls reporting units during the second quarter of 2018. The Company elected to perform a qualitative assessment (commonly known as "step zero") for the purposes of its annual goodwill impairment analysis for the Vinyls reporting units. Based upon this assessment, the Company determined that it is more likely than not that the fair value of each of the Vinyls reporting units exceeds its carrying value. Factors considered in the qualitative assessment included macroeconomic conditions, industry and market considerations, cost factors related to raw materials and labor, overall financial performance (both current and projected), changes in management or strategy, and market capitalization.

Long-Term Debt

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Long-Term Debt

Long-term debt consists of the following:



	September 30, 2018							December 31, 2017
	Principal Amount		Unamortized Discount and Debt Issuance Costs			Net Long-term Debt		Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt
3.60% senior notes due 2022 (the "3.60% 2022 Senior Notes")	$	250	$	(1	)	$	249	$	250	$	(1	)	$	249
3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes")	750		(9		)	741		750		(10		)	740
Loan related to tax-exempt waste disposal revenue bonds due 2027	11		—			11		11		—			11
6 ½% senior notes due 2029 (the "6 ½% 2029 GO Zone Senior Notes")	100		(1		)	99		100		(1		)	99
6 ½% senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes")	89		(1		)	88		89		(1		)	88
6 ½% senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes")	65		—			65		65		—			65
5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes")	700		(25		)	675		700		(25		)	675
4.375% senior notes due 2047 (the "4.375% 2047 Senior Notes")	500		(9		)	491		500		(9		)	491
3.50% senior notes due 2032 (the "3.50% 2032 GO Zone Refunding Senior Notes")	250		(2		)	248		250		(2		)	248
4.625% senior notes due 2021 (the "4.625% Westlake 2021 Senior Notes")	—		—			—		625		20			645
4.625% senior notes due 2021 (the "4.625% Subsidiary 2021 Senior Notes")	—		—			—		63		2			65
4.875% senior notes due 2023 (the "4.875% Westlake 2023 Senior Notes")	—		—			—		434		11			445
4.875% senior notes due 2023 (the "4.875% Subsidiary 2023 Senior Notes")	—		—			—		16		—			16
Total Long-term debt	2,715		(48		)	2,667		3,853		(16		)	3,837
Less:
Current portion - 4.625% Westlake 2021 Senior Notes and 4.625% Subsidiary 2021 Senior Notes	—		—			—		688		22			710
Long-term debt, net of current portion	$	2,715	$	(48	)	$	2,667	$	3,165	$	(38	)	$	3,127

New Credit Agreement

On July 24, 2018, the Company entered into a new $1,000 revolving credit facility that is scheduled to mature on July 24, 2023 (the "New Credit Agreement") and, in connection therewith, terminated the existing $1,000 revolving credit facility that was scheduled to mature on August 23, 2021. The New Credit Agreement bears interest at either (a) LIBOR plus a spread ranging from 1.00% to 1.75% or (b) Alternate Base Rate plus a spread ranging from 0.00% to 0.75% in each case depending on the credit rating of the Company. At September 30, 2018, the Company had no borrowings outstanding under the New Credit Agreement. As of September 30, 2018, the Company had outstanding letters of credit totaling $4 and borrowing availability of $996 under the New Credit Agreement. The New Credit Agreement contains certain affirmative and negative covenants, including a quarterly total leverage ratio financial maintenance covenant. As of September 30, 2018, the Company was in compliance with the total leverage ratio financial maintenance covenant. The New Credit Agreement also contains certain events of default and if and for so long as certain events of default have occurred and are continuing, any overdue amounts outstanding under the New Credit Agreement will accrue interest at an increased rate, the lenders can terminate their commitments thereunder and payments of any outstanding amounts could be accelerated by the lenders. None of the Company's subsidiaries are required to guarantee the obligations of the Company under the New Credit Agreement.

The New Credit Agreement includes a $150 sub-limit for letters of credit, and any outstanding letters of credit will be deducted from availability under the facility. The New Credit Agreement also provides for a discretionary $50 commitment for swingline loans to be provided on a same-day basis. The Company may also increase the size of the facility, in increments of at least $25, up to a maximum of $500, subject to certain conditions and if certain lenders agree to commit to such an increase.

In connection with the Company's entry into the New Credit Agreement and termination of the prior credit agreement on July 24, 2018, all guarantees by the Guarantor Subsidiaries of the Company's payment obligations under the 4.375% 2047 Senior Notes, the 3.60% 2022 Senior Notes, the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes were released. As a result, beginning with this quarterly report on Form 10-Q, the Company no longer discloses condensed consolidating financial information of its guarantor and non-guarantor subsidiaries.

4.625% Senior Notes due 2021

In December 2017, the Company delivered irrevocable notices for the optional redemption of all of the outstanding 4.625% Westlake 2021 Senior Notes and 4.625% Subsidiary 2021 Senior Notes (collectively, the "2021 Notes"). The 2021 Notes were redeemed on February 15, 2018 at a redemption price equal to 102.313% of the principal amount of the 2021 Notes plus accrued and unpaid interest on the 2021 Notes to the redemption date. The Company recognized a $6 gain in other income upon redemption of the 2021 Notes.

4.875% Senior Notes due 2023

In March 2018, the Company delivered irrevocable notices for the optional redemption of all of the outstanding 4.875% Westlake 2023 Senior Notes and 4.875% Subsidiary 2023 Senior Notes (collectively, the "2023 Notes"). The 2023 Notes were redeemed on May 15, 2018 at a redemption price equal to 102.438% of the principal amount of the 2023 Notes plus accrued and unpaid interest on the 2023 Notes to the redemption date.

As of September 30, 2018, the Company was in compliance with all of its long-term debt covenants.

Unamortized debt issuance costs on long-term debt were $26 and $26 at September 30, 2018 and December 31, 2017, respectively.

Pension and Post-Retirement Benefits Pension and Post-Retirement Benefits

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Pension and Other Postretirement Benefits Disclosure [Text Block]

7. Pension and Post-Retirement Benefits

Defined Benefit Plans

Components of net periodic benefit cost (income) for the Company's pension plans are as follows:



	Three Months Ended September 30,										Nine Months Ended September 30,
	2018					2017					2018					2017
	U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans
Service cost	$	1		$	—	$	2		$	—	$	2		$	1	$	4		$	1
Expected administrative expenses	1			—		—			—		2			—		—			—
Interest cost	6			1		6			1		18			2		19			2
Expected return on plan assets	(10		)	—		(10		)	—		(32		)	—		(30		)	—
Amortization of net loss	—			—		—			—		—			—		1			—
Settlement gain	(14		)	—		—			—		(14		)	—		—			—
Net periodic benefit cost (income)	$	(16	)	$	1	$	(2	)	$	1	$	(24	)	$	3	$	(6	)	$	3

During the third quarter of 2018, the Company's U.S. pension plans settled portions of their projected benefit obligations through the purchase of annuities and lump sum payments to certain participants. In conjunction with the settlement, the Company also remeasured the pension obligations and plan assets of the affected plans, resulting in a $26 increase in accumulated other comprehensive income before tax and a corresponding decrease in net pension liabilities recorded in the consolidated balance sheets. The Company recognized a $14 one-time settlement gain in other income, net, which was reclassified from accumulated other comprehensive income.

Accumulated Other Comprehensive Income (Loss) (Notes)

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Comprehensive Income (Loss) Note [Text Block]

Accumulated Other Comprehensive Income (Loss)

Changes in accumulated other comprehensive income (loss) by component for the nine months ended September 30, 2018 and 2017 were as follows:



	Benefits Liability, Net of Tax			Cumulative Foreign Currency Exchange, Net of Tax			Total
Balances at December 31, 2016	$	29		$	(150	)	$	(121	)
Other comprehensive income before reclassifications	—			107			107
Amounts reclassified from accumulated other comprehensive income (loss)	1			—			1
Net other comprehensive income attributable to Westlake Chemical Corporation	1			107			108
Balances at September 30, 2017	$	30		$	(43	)	$	(13	)

Balances at December 31, 2017	$	43		$	(36	)	$	7
Other comprehensive income (loss) before reclassifications	20			(40		)	(20		)
Amounts reclassified from accumulated other comprehensive income (loss)	(11		)	—			(11		)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	9			(40		)	(31		)
Balances at September 30, 2018	$	52		$	(76	)	$	(24	)

The following table provides the details of the amounts reclassified from accumulated other comprehensive income (loss) into net income in the consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017:



Details about Accumulated Other Comprehensive Income (Loss) Components	Location of Reclassification (Income (Expense)) in Consolidated Statements of Operations	Three Months Ended September 30,						Nine Months Ended September 30,
		2018			2017			2018			2017
Amortization of pension and other post-retirement net loss	(1)	$	—		$	(1	)	$	—		$	(2	)
Pension settlement gain	(1)	14			—			14			—
Income tax provision on pension and other post-retirement benefits liability	Benefits from (provision for) income taxes	(3		)	1			(3		)	1
Total reclassifications for the period		$	11		$	—		$	11		$	(1	)

_____________


(1)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost and reflected in other income, net in the consolidated statements of operations. See Note 7 for additional information on the pension settlement gain.

Fair Value Measurements

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

The Company reports certain assets and liabilities at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). Under the accounting guidance for fair value measurements, inputs used to measure fair value are classified in one of three levels:

Level 1: Quoted market prices in active markets for identical assets or liabilities.

Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data.

Level 3: Unobservable inputs that are not corroborated by market data.

The Company has financial assets and liabilities subject to fair value measures. These financial assets and liabilities include cash and cash equivalents, accounts receivable, net, accounts payable and long-term debt, all of which are recorded at carrying value. The amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, net and accounts payable approximate their fair value due to the short maturities of these instruments.

The carrying and fair values of the Company's long-term debt (including the current portion of long-term debt) are summarized in the table below. The Company's long-term debt instruments are publicly-traded. A market approach, based upon quotes from financial reporting services, is used to measure the fair value of the Company's long-term debt. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy.



	September 30, 2018				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value
3.60% 2022 Senior Notes	$	249	$	246	$	249	$	255
3.60% 2026 Senior Notes	741		704		740		757
Loan related to tax-exempt waste disposal revenue bonds due 2027	11		11		11		11
6 ½% 2029 GO Zone Senior Notes	99		108		99		111
6 ½% 2035 GO Zone Senior Notes	88		96		88		99
6 ½% 2035 IKE Zone Senior Notes	65		70		65		74
5.0% 2046 Senior Notes	675		687		675		787
4.375% 2047 Senior Notes	491		446		491		518
3.50% 2032 GO Zone Refunding Senior Notes	248		241		248		256
4.625% Westlake 2021 Senior Notes	—		—		645		639
4.625% Subsidiary 2021 Senior Notes	—		—		65		65
4.875% Westlake 2023 Senior Notes	—		—		445		449
4.875% Subsidiary 2023 Senior Notes	—		—		16		16

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rate was 18.7% for the third quarter of 2018 as compared to the effective income tax rate of 33.1% for the third quarter of 2017. The lower tax rate in the third quarter of 2018 as compared to the third quarter of 2017 was primarily a result of the tax law changes enacted under the Tax Act, which was signed into law on December 22, 2017. The effective income tax rate for the third quarter of 2018 was below the U.S. federal statutory rate of 21.0% primarily due to certain discrete tax benefit adjustments related to the re-measurement of state deferred tax balances and change in income tax estimate due to the filing of the Company's 2017 U.S. federal tax return. The effective income tax rate for the third quarter of 2017 was below the U.S. federal statutory rate of 35.0% primarily due to a higher domestic manufacturing deduction, depletion deductions, income attributable to noncontrolling interests, research and development credits and the foreign earnings rate differential, partially offset by state income taxes. The effective income tax rate was 22.0% for the nine months ended September 30, 2018. The effective income tax rate for the nine months ended September 30, 2018 was above the U.S. federal statutory rate of 21.0% primarily due to state and foreign taxes. The effective income tax rate was 30.8% for the nine months ended September 30, 2017. The effective income tax rate for the 2017 period was below the U.S. federal statutory rate of 35.0% primarily due to certain discrete adjustments, a higher domestic manufacturing deduction, depletion deductions, income attributable to noncontrolling interests, research and development credits and the foreign earnings rate differential, partially offset by state income taxes. The Tax Act, among other changes, reduced U.S. corporate income tax rate from 35.0% to 21.0%, effective January 1, 2018, and also required a one-time deemed repatriation of foreign earnings at specified rates. The accounting guidance on income taxes requires that the effect on deferred tax assets and liabilities of a change in tax rates be recognized in the period the tax rate change was enacted. The SEC staff guidance allows registrants to record provisional amounts during a measurement period when it does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete its accounting for the change in tax law. The measurement period ends when a company has obtained, prepared and analyzed the information necessary to finalize its accounting, but cannot extend beyond one year. The corporate income tax rate change resulted in a revaluation of the Company's deferred tax assets and liabilities. At December 31, 2017, under the above guidance, the Company made a provisional adjustment of $591 of income tax benefit in the 2017 consolidated financial statements for items that the Company could reasonably estimate such as revaluation of deferred tax assets and liabilities and a one-time U.S. tax on the mandatory deemed repatriation of the Company's post-1986 foreign earnings. The Company will continue to assess the income tax effects of the Tax Act based on further standard setting activities, any transition provisions, and changes in the facts and circumstances of the Company's tax position, during the measurement period. No measurement period adjustment was made for the nine months ended September 30, 2018.

Earnings and Dividends per Share

9 Months Ended

Sep. 30, 2018

Earnings Per Share [Abstract]

Earnings per Share

Earnings and Dividends per Share

Earnings per Share

The Company has unvested restricted stock units outstanding that are considered participating securities and, therefore, computes basic and diluted earnings per share under the two-class method. Basic earnings per share for the periods are based upon the weighted average number of shares of common stock outstanding during the periods. Diluted earnings per share includes the effect of certain stock options.



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Net income attributable to Westlake Chemical Corporation	$	308		$	211		$	873		$	502
Less:
Net income attributable to participating securities	(1		)	(1		)	(4		)	(3		)
Net income attributable to common shareholders	$	307		$	210		$	869		$	499

The following table reconciles the denominator for the basic and diluted earnings per share computations shown in the consolidated statements of operations:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Weighted average common shares—basic	129,427,328		129,069,186		129,512,097		129,033,597
Plus incremental shares from:
Assumed exercise of options	624,964		819,782		671,104		756,368
Weighted average common shares—diluted	130,052,292		129,888,968		130,183,201		129,789,965

Earnings per common share attributable to Westlake Chemical Corporation:
Basic	$	2.36	$	1.62	$	6.70	$	3.87
Diluted	$	2.35	$	1.61	$	6.67	$	3.85

Excluded from the computation of diluted earnings per share are options to purchase 172,194 and 335,276 shares of common stock for the three months ended September 30, 2018 and 2017, respectively, and 143,439 and 291,888 shares of common stock for the nine months ended September 30, 2018 and 2017, respectively. These options were outstanding during the periods reported but were excluded because the effect of including them would have been antidilutive.

Dividends per Share

Dividends per common share for the three months ended September 30, 2018 and 2017 and for the nine months ended September 30, 2018 and 2017 were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Dividends per common share	$	0.2500	$	0.2100	$	0.6700	$	0.5912

Supplemental Information	9 Months Ended
Supplemental Information	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information Accrued Liabilities Accrued liabilities were $675 and $657 at September 30, 2018 and December 31, 2017, respectively. Accrued rebates, which are components of accrued liabilities, were $112 and $108 at September 30, 2018 and December 31, 2017, respectively. No other component of accrued liabilities was more than five percent of total current liabilities. Accrued liabilities with affiliates were $45 and $37 at September 30, 2018 and December 31, 2017, respectively. Non-cash Investing Activity The change in capital expenditure accrual resulted in a decrease in additions to property, plant and equipment by $8 for the nine months ended September 30, 2018. The change in capital expenditure accrual resulted in an increase in additions to property, plant and equipment by $8 for the nine months ended September 30, 2017. Other Income, Net For the three months ended September 30, 2018, other income, net included income from pension and postretirement plans, including a one-time settlement gain, income from unconsolidated subsidiaries and interest income on cash and cash equivalents of $16, $5 and $4, respectively. For the three months ended September 30, 2017, other income, net included income from pension and postretirement plans, income from unconsolidated subsidiaries and interest income on cash and cash equivalents of $2, $4 and $1, respectively. For the nine months ended September 30, 2018 other income, net included income from pension and postretirement plans, including a one-time settlement gain, gain on redemption of the 2021 Notes, income from unconsolidated subsidiaries and interest income on cash and cash equivalents of $23, $6, $17 and $13, respectively. For the nine months ended September 30, 2017, other income, net included income from pension and postretirement plans, income from unconsolidated subsidiaries and interest income on cash and cash equivalents of $6, $11 and $2, respectively.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company is involved in a number of legal and regulatory matters, principally environmental in nature, that are incidental to the normal conduct of its business, including lawsuits, investigations and claims. The outcomes of these matters are inherently unpredictable. The Company believes that, in the aggregate, the outcome of all known legal and regulatory matters will not have a material adverse effect on its consolidated financial statements; however, specific outcomes with respect to such matters may be material to the Company's consolidated statements of operations in any particular period in which costs, if any, are recognized. The Company's assessment of the potential impact of environmental matters, in particular, is subject to uncertainty due to the complex, ongoing and evolving process of investigation and remediation of such environmental matters, and the potential for technological and regulatory developments. In addition, the impact of evolving claims and programs, such as natural resource damage claims, industrial site reuse initiatives and state remediation programs creates further uncertainty of the ultimate resolution of these matters. The Company anticipates that the resolution of many legal and regulatory matters, and in particular environmental matters, will occur over an extended period of time. Environmental. As of September 30, 2018 and December 31, 2017, the Company had reserves for environmental contingencies totaling approximately $57 and $49, respectively, most of which were classified as noncurrent liabilities. The Company's assessment of the potential impact of these environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. Calvert City Proceedings. For several years, the Environmental Protection Agency (the "EPA") has been conducting remedial investigation and feasibility studies at the Company's Calvert City, Kentucky facility pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 ("CERCLA"). As the current owner of the Calvert City facility, the Company was named by the EPA as a potentially responsible party ("PRP") along with Goodrich Corporation ("Goodrich") and its successor-in-interest, PolyOne Corporation ("PolyOne"). On November 30, 2017, the EPA published a draft Proposed Plan, incorporating by reference an August 2015 draft Remedial Investigation ("RI") report, an October 2017 draft Feasibility Study ("FS") report and a new Technical Impracticability Waiver document dated December 19, 2017. The draft Proposed Plan described a preferred remedy that included a containment wall with targeted treatment and supplemental hydraulic containment, as well as active treatment of historical groundwater contamination under the Tennessee River. The EPA estimated that the total remedy would cost $200 to $250 with an estimated $1 to $3 in annual operation and maintenance ("O&M") costs. Each PRP, including the Company, submitted comments to the Proposed Plan and associated documents. The Company's comments also proposed alternative removal options for the groundwater contamination under the Tennessee River. On June 18, 2018, the EPA published an amendment to its Proposed Plan. The amended Proposed Plan addresses the comments filed on the river excavation remedy outlined in the original Proposed Plan. Under the amended Proposed Plan, the EPA proposes an interim approach to address the contamination under the river that would include recovery of any mobile contaminants by an extraction well along with further study of the extent of the contamination and potential treatment options. The EPA's revised estimated cost of implementation is $107, with the estimated annual O&M costs remaining unchanged. In September 2018, the EPA published the EPA's section of the final containment remedy for the on shore portion of the site and the interim remedy for the contamination under the river, as outlined in the amended Proposed Plan. The Company's allocation of liability for remedial or O&M costs, if any, will be determined by the outcome of the contractual dispute with Goodrich/PolyOne, which is the subject of a pending arbitration proceeding as described below. In connection with the 1990 and 1997 acquisitions of the Goodrich chemical manufacturing complex in Calvert City, Goodrich agreed to indemnify the Company for any liabilities related to preexisting contamination at the complex. For its part, the Company agreed to indemnify Goodrich for post-closing contamination caused by the Company's operations. The soil and groundwater at the complex, which does not include the Company's nearby PVC facility, had been extensively contaminated by Goodrich's operations. In 1993, Goodrich spun off the predecessor of PolyOne, and that predecessor assumed Goodrich's indemnification obligations relating to preexisting contamination. In 2003, litigation arose among the Company, Goodrich and PolyOne with respect to the allocation of the cost of remediating contamination at the site. The parties settled this litigation in December 2007 and the case was dismissed. In the settlement, the parties agreed that, among other things: (1) PolyOne would pay 100% of the costs (with specified exceptions), net of recoveries or credits from third parties, incurred with respect to environmental issues at the Calvert City site from August 1, 2007 forward; and (2) either the Company or PolyOne might, from time to time in the future (but not more than once every five years), institute an arbitration proceeding to adjust that percentage. In May 2017, PolyOne filed a demand for arbitration. In this proceeding, PolyOne seeks to readjust the percentage allocation of costs and to recover approximately $17 from the Company in reimbursement of previously paid remediation costs. The Company has filed a cross demand for arbitration seeking unreimbursed remediation costs incurred during the relevant period. On October 6, 2017, PolyOne filed suit against the Company in the U.S. District Court for the Western District of Kentucky seeking for the court, instead of the arbitration panel, to resolve claims asserted by the Company in the arbitration proceedings related to reimbursement of costs incurred by the Company at the Calvert City complex. On May 30, 2018, the U.S. District Court for the Western District of Kentucky granted the Company's motion to dismiss, concluding that all of PolyOne's claims were the proper subject of the current arbitration panel's jurisdiction, and dismissed PolyOne's action before the court. On July 10, 2018, PolyOne filed another action in the U.S. District Court for the Western District of Kentucky, seeking for the court to issue an injunction against continued proceedings in the arbitration. On July 30, 2018, the Court denied PolyOne's motion for a temporary restraining order and preliminary injunction. The arbitration hearing began in August 2018 and is ongoing. At this time, the Company is not able to estimate the impact, if any, that the arbitration proceeding could have on the Company's consolidated financial statements either in the current period or in later periods. Any cash expenditures that the Company might incur in the future with respect to the remediation of contamination at the Calvert City complex would likely be spread out over an extended period. As a result, the Company believes it is unlikely that any remediation costs allocable to it will be material in terms of expenditures made in any individual reporting period. Environmental Remediation: Reasonably Possible Matters. The Company's assessment of the potential impact of environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. As such, in addition to the amounts currently reserved, the Company may be subject to reasonably possible loss contingencies related to environmental matters in the range of $55 to $110. Commitments. The Company became a party to a joint venture investment with Lotte Chemical USA Corporation to build an ethylene facility, LACC. The ethylene facility is located adjacent to the Company's vinyls facility in Lake Charles. Pursuant to the contribution and subscription agreement, the Company agreed to make a maximum capital commitment to LACC of up to $225 to fund the construction costs of the ethylene plant, which represents approximately 10% of the interests in LACC. The construction of the ethylene plant commenced in January 2016, with an anticipated start-up in 2019. As of September 30, 2018, the Company had funded approximately $178 of the Company's portion of the construction costs of the ethylene plant.

Segment Information

9 Months Ended

Sep. 30, 2018

Segment Reporting [Abstract]

Segment Information

The Company operates in two principal operating segments: Olefins and Vinyls. These segments are strategic business units that offer a variety of different products. The Company manages each segment separately as each business requires different technology and marketing strategies.



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Net external sales
Olefins
Polyethylene	$	396		$	377		$	1,152		$	1,121
Styrene, feedstock and other	145			125			374			413
Total Olefins	541			502			1,526			1,534
Vinyls
PVC, caustic soda and other	1,372			1,253			4,126			3,541
Building products	342			354			988			956
Total Vinyls	1,714			1,607			5,114			4,497
	$	2,255		$	2,109		$	6,640		$	6,031

Intersegment sales
Olefins	$	136		$	107		$	368		$	291
Vinyls	—			1			1			1
	$	136		$	108		$	369		$	292

Income (loss) from operations
Olefins	$	162		$	166		$	483		$	489
Vinyls	251			214			788			425
Corporate and other	(17		)	(16		)	(70		)	(52		)
	$	396		$	364		$	1,201		$	862

Depreciation and amortization
Olefins	$	35		$	35		$	102		$	111
Vinyls	124			118			362			332
Corporate and other	2			1			9			6
	$	161		$	154		$	473		$	449

Other income, net
Olefins	$	1		$	—		$	4		$	2
Vinyls	16			1			32			7
Corporate and other	6			3			17			4
	$	23		$	4		$	53		$	13

Provision for (benefit from) income taxes
Olefins	$	34		$	58		$	107		$	152
Vinyls	44			61			174			115
Corporate and other	(5		)	(10		)	(26		)	(34		)
	$	73		$	109		$	255		$	233



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Capital expenditures
Olefins	$	33	$	21	$	81	$	70
Vinyls	162		108		420		330
Corporate and other	—		4		6		14
	$	195	$	133	$	507	$	414

A reconciliation of total segment income from operations to consolidated income before income taxes is as follows:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Income from operations	$	396		$	364		$	1,201		$	862
Interest expense	(28		)	(40		)	(96		)	(119		)
Other income, net	23			4			53			13
Income before income taxes	$	391		$	328		$	1,158		$	756



	September 30, 2018		December 31, 2017
Total assets
Olefins	$	2,074	$	2,006
Vinyls	8,953		8,853
Corporate and other	694		1,217
	$	11,721	$	12,076

Westlake Chemical Partners LP (Notes)

9 Months Ended

Sep. 30, 2018

Partners' Capital [Abstract]

Westlake Chemical Partners LP

The Company has an 81.7% limited partner interest in Westlake Chemical OpCo LP ("OpCo"), a 43.8% limited partner interest in Westlake Chemical Partners LP ("Westlake Partners"), a general partner interest in Westlake Partners and incentive distribution rights ("IDRs"). On July 27, 2018, the Westlake Partners' partnership agreement was amended to revise the minimum quarterly distribution thresholds for Westlake Partners' IDRs. The amended agreement provides that Westlake Partners will distribute cash each quarter to all the unitholders, pro rata, until each unit has received a distribution of $1.2938. If cash distributions to Westlake Partners' unitholders exceed $1.2938 per unit in any quarter, Westlake Partners' unitholders and Westlake, as the holder of the Westlake Partners' incentive distribution rights, will receive distributions according to the following percentage allocations per the amendment:



	Marginal Percentage Interest in Distributions
Total Quarterly Distribution Per Unit	Unitholders		IDR Holders
Above $1.2938 up to $1.4063	85.0	%	15.0	%
Above $1.4063 up to $1.6875	75.0	%	25.0	%
Above $1.6875	50.0	%	50.0	%

The Westlake Partners' distribution for the three months ended September 30, 2018 did not exceed the $1.2938 per unit threshold, and, as a result of the amendment, no distribution was made with respect to Westlake Partners' IDRs to Westlake, as the holder of the Westlake Partners' IDRs.

Prior to the amendment, Westlake Partners' partnership agreement provided that Westlake Partners' unitholders and Westlake, as the holder of Westlake Partners' IDRs, would receive distributions according to the following percentage allocations:



	Marginal Percentage Interest in Distributions
Total Quarterly Distribution Per Unit	Unitholders		IDR Holders
Above $0.3163 up to $0.3438	85.0	%	15.0	%
Above $0.3438 up to $0.4125	75.0	%	25.0	%
Above $0.4125	50.0	%	50.0	%

Subsequent Events (Notes)	9 Months Ended
Subsequent Events (Notes)	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events On October 4, 2018, Westlake Partners and Westlake Chemical Partners GP LLC, the general partner of Westlake Partners, entered into an Equity Distribution Agreement with UBS Securities LLC, Barclays Capital Inc., Citigroup Global Markets Inc., Deutsche Bank Securities Inc., RBC Capital Markets, LLC, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Wells Fargo Securities, LLC to offer and sell Westlake Partners' common units, from time to time, up to an aggregate offering amount of $50.

Basis of Financial Statements (Policies)	9 Months Ended
Basis of Financial Statements (Policies)	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Financial Statements	The accompanying unaudited consolidated interim financial statements were prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim periods. Accordingly, certain information and footnotes required for complete financial statements under generally accepted accounting principles in the United States ("U.S. GAAP") have not been included. These interim consolidated financial statements should be read in conjunction with the December 31, 2017 consolidated financial statements and notes thereto of Westlake Chemical Corporation (the "Company") included in the annual report on Form 10-K for the fiscal year ended December 31, 2017 (the "2017 Form 10-K"), filed with the SEC on February 21, 2018. These consolidated financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Company for the fiscal year ended December 31, 2017 with the exception of those accounting standards adopted in 2018 as discussed in Note 1. In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of September 30, 2018, its results of operations for the three and nine months ended September 30, 2018 and 2017 and the changes in its cash position for the nine months ended September 30, 2018 and 2017. Results of operations and changes in cash position for the interim periods presented are not necessarily indicative of the results that will be realized for the fiscal year ending December 31, 2018 or any other interim period. The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Certain reclassifications have been made to the prior-year financial statements to conform to the current-year presentation.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Leases (ASU No. 2016-02) In February 2016, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The standard requires adoption using a modified retrospective approach and allows for the election of certain transition practical expedients. The accounting standards update allows for certain transition expedients for leases that commenced prior to the adoption of the new standard. Under the optional transition expedients an entity is not required to reassess (1) whether any expired or existing lease contracts are or contain leases, (2) the classification of leases as operating or capital leases or (3) whether any initial direct costs qualify for capitalization under the new accounting standard. These expedients are required to be elected as a group. The accounting standards update also allows the use of hindsight to determine lease term when considering lease renewal or termination options. During 2018, the FASB issued additional authoritative guidance that provides an optional transition method which allows entities to continue applying the existing lease guidance in the comparative periods and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The FASB also issued an accounting standards update that allows entities to apply their existing policy for accounting for land easements that exist as of, or expired before, the effective date of the new lease standard. The Company is in the process of evaluating the transition method and other expedients it may elect. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Company is in the process of reviewing its existing lease agreements and evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Income Statement - Reporting Comprehensive Income (ASU 2018-02) In February 2018, the FASB issued an accounting standards update to (1) allow reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the U.S. Tax Cuts and Jobs Act (the "Tax Act"); and (2) require certain disclosures about stranded tax effects. The accounting standard will be effective for reporting periods beginning after December 15, 2018. Early adoption is permitted. The Company is in the process of evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Fair Value Measurement (ASU No. 2018-13) In August 2018, the FASB issued an accounting standards update to modify the disclosure requirements on fair value measurements. The amendments are effective beginning after December 15, 2019. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until the effective date. Most amendments should be applied retrospectively, but certain amendments will be applied prospectively. The Company is in the process of assessing the impact of the standard on the Company's fair value disclosures. However, the standard is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2018-15) In August 2018, the FASB issued an accounting standards update to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). The amendments are effective for fiscal years beginning after December 15, 2019 and early adoption is permitted. The amendments should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company adopted the standard on October 1, 2018, prospectively, and did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standards Revenue from Contracts with Customers (ASU No. 2014-09) In May 2014, the FASB issued an accounting standards update on a comprehensive new revenue recognition standard that supersedes virtually all previously issued revenue recognition guidance. The new accounting guidance creates a framework by which an entity will allocate the transaction price to separate performance obligations and recognize revenue when each performance obligation is satisfied. Under the new standard, entities are required to use judgment and make estimates, including identifying performance obligations in a contract, estimating the amount of variable consideration to include in the transaction price, allocating the transaction price to each separate performance obligation and determining when an entity satisfies its performance obligations. The standard allows for "modified retrospective" adoption, meaning the standard is applied only to the most current period presented in the financial statements with a cumulative catch-up as of the current period. The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers ("ASC 606"), effective January 1, 2018. The Company applied the modified retrospective transition method to all contracts that were not completed as of the adoption date. Periods prior to January 1, 2018 were not adjusted and are reported under the accounting standards that were in place during those periods. The cumulative effects of changes to the Company's consolidated January 1, 2018 balance sheet for the adoption of this accounting standard were immaterial. The impact of ASC 606 adoption on the financial statements for the three and nine months ended September 30, 2017 as compared with the guidance that was in effect prior to January 1, 2018 was immaterial. Revenue is recognized when the Company transfers control of inventories to its customers. Amounts recognized as revenues reflect the consideration to which the Company expects to be entitled in exchange for those inventories. Provisions for discounts, rebates and returns are incorporated in the estimate of variable consideration and reflected as reduction to revenue in the same period as the related sales. Control of inventories generally transfers upon shipment for domestic sales. The Company excludes taxes collected on behalf of customers from the estimated contract price. For export contracts, the point at which control passes to the customer varies depending on the terms specified in the customer contract. The Company generally invoices customers and recognizes revenue and accounts receivable upon transferring control of inventories. In limited circumstances, the Company transfers control of inventories shortly before it has an unconditional right to receive consideration, resulting in recognition of contract assets. The Company also receives advance payments from certain customers, resulting in recognition of contract liabilities. Contract assets and liabilities are generally settled within the period and are not material to the consolidated balance sheets. The Company expenses sales commissions when incurred. These costs are recorded within selling, general and administrative expenses. The Company does not disclose the value of unsatisfied performance obligations because its contracts with customers (i) have an original expected duration of one year or less or (ii) have only variable consideration that is calculated based on market prices at specified dates and is allocated to wholly unsatisfied performance obligations. ASC 606 requires disclosure of disaggregated revenue into categories that depict the nature of how the Company's revenue and cash flows are affected by economic factors. The Company discloses revenues by product and segment in Note 14 to this quarterly report on Form 10-Q. Recognition and Measurement of Financial Assets and Financial Liabilities (ASU No. 2016-01) In January 2016, the FASB issued an accounting standards update making certain changes principally to the current guidance for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. Among other things, the guidance (1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value, with changes in fair value recognized in net income; (2) allows entities to elect to measure equity investments without readily determinable fair values at cost, less impairment, adjusted for subsequent observable price changes (changes in the basis of these equity investments to be reported in net income); (3) requires an entity that has elected the fair value option for financial liabilities to recognize changes in fair value due to instrument-specific credit risk separately in other comprehensive income; (4) clarified current guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities; and (5) requires specific disclosure pertaining to financial assets and financial liabilities in the financial statements. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. The Company is party to a joint venture investment with Lotte Chemical USA Corporation to build an ethylene facility, LACC, LLC ("LACC"). The Company measures its investment in LACC at cost, adjusted for observable price changes because the investment does not have a readily determinable fair value. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-18) In November 2016, the FASB issued an accounting standards update to clarify certain existing principles in Accounting Standards Codification 230, Cash flows, including providing additional guidance related to transfers between cash and restricted cash and how entities present, in their statement of cash flows, the cash receipts and cash payments that directly affect the restricted cash accounts. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018. Upon adoption, the Company retrospectively adjusted its financial statements to reflect restricted cash in the beginning and ending cash and restricted cash balances within the statements of cash flows. As a result of this retrospective adoption and reclassification of restricted cash and cash equivalents, net cash provided by (used for) financing activities on the consolidated statement of cash flows for the nine months ended September 30, 2017 has been adjusted to $(460) from the originally reported $(306) to reflect the retrospective application of the new accounting guidance. Previously reported cash and cash equivalents at beginning of the period and cash and cash equivalents at end of the period for the nine months ended September 30, 2017 have been adjusted to include restricted cash of $186 and $32, respectively. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in ASC 606. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted the accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income—gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Retirement Benefits (ASU No. 2017-07) In March 2017, the FASB issued an accounting standards update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires employers to disaggregate the service cost component from the other components of net periodic benefit cost and report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The amendments also allow only the service cost component to be eligible for capitalization when applicable. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Stock Compensation (ASU No. 2017-09) In May 2017, the FASB issued an accounting standards update to provide clarity and reduce both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require the application of modification accounting in Topic 718. Essentially, an entity will not have to account for the effects of a modification if: (1) the fair value of the modified award is the same immediately before and after the modification; (2) the vesting conditions of the modified award are the same immediately before and after the modification; and (3) the classification of the modified award as either an equity instrument or liability instrument is the same immediately before and after the modification. This update is to be applied prospectively to an award modified on or after the adoption date. The accounting standard became effective for reporting periods beginning after December 15, 2017. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities (ASU No. 2017-12) In August 2017, the FASB issued an accounting standards update to improve financial reporting of hedging relationships, to better portray the economic results of an entity's risk management activities in the financial statements and to simplify application of hedge accounting guidance. The accounting standard eliminates certain hedge effectiveness measurement and reporting requirements and expands the types of permissible hedging strategies. The accounting standard will be effective for reporting periods beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance, to be applied retrospectively to the beginning of the fiscal year. The Company adopted this accounting standard effective January 1, 2018 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows.

Accounts Receivable (Tables)

9 Months Ended

Sep. 30, 2018

Accounts Receivable, Net [Abstract]

Schedule Of Accounts Receivable

Accounts receivable consist of the following:



	September 30, 2018			December 31, 2017
Trade customers	$	1,171		$	974
Affiliates	11			9
Allowance for doubtful accounts	(24		)	(22		)
	1,158			961
Federal and state taxes	55			7
Other	28			33
Accounts receivable, net	$	1,241		$	1,001

Inventories (Tables)

9 Months Ended

Sep. 30, 2018

Inventory Disclosure [Abstract]

Schedule Of Inventory

Inventories consist of the following:



	September 30, 2018		December 31, 2017
Finished products	$	566	$	549
Feedstock, additives, chemicals and other raw materials	221		221
Materials and supplies	152		130
Inventories	$	939	$	900

Goodwill (Tables)

9 Months Ended

Sep. 30, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill [Table Text Block]

The gross carrying amounts and changes in the carrying amount of goodwill for the nine months ended September 30, 2018 were as follows:



	Olefins Segment		Vinyls Segment			Total
Balances at December 31, 2017	$	30	$	982		$	1,012
Effects of changes in foreign exchange rates	—		(4		)	(4		)
Balances at September 30, 2018	$	30	$	978		$	1,008

Long-Term Debt (Tables)

9 Months Ended

Sep. 30, 2018

Debt Disclosure [Abstract]

Schedule Of Long-Term Debt

Long-term debt consists of the following:



	September 30, 2018							December 31, 2017
	Principal Amount		Unamortized Discount and Debt Issuance Costs			Net Long-term Debt		Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt
3.60% senior notes due 2022 (the "3.60% 2022 Senior Notes")	$	250	$	(1	)	$	249	$	250	$	(1	)	$	249
3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes")	750		(9		)	741		750		(10		)	740
Loan related to tax-exempt waste disposal revenue bonds due 2027	11		—			11		11		—			11
6 ½% senior notes due 2029 (the "6 ½% 2029 GO Zone Senior Notes")	100		(1		)	99		100		(1		)	99
6 ½% senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes")	89		(1		)	88		89		(1		)	88
6 ½% senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes")	65		—			65		65		—			65
5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes")	700		(25		)	675		700		(25		)	675
4.375% senior notes due 2047 (the "4.375% 2047 Senior Notes")	500		(9		)	491		500		(9		)	491
3.50% senior notes due 2032 (the "3.50% 2032 GO Zone Refunding Senior Notes")	250		(2		)	248		250		(2		)	248
4.625% senior notes due 2021 (the "4.625% Westlake 2021 Senior Notes")	—		—			—		625		20			645
4.625% senior notes due 2021 (the "4.625% Subsidiary 2021 Senior Notes")	—		—			—		63		2			65
4.875% senior notes due 2023 (the "4.875% Westlake 2023 Senior Notes")	—		—			—		434		11			445
4.875% senior notes due 2023 (the "4.875% Subsidiary 2023 Senior Notes")	—		—			—		16		—			16
Total Long-term debt	2,715		(48		)	2,667		3,853		(16		)	3,837
Less:
Current portion - 4.625% Westlake 2021 Senior Notes and 4.625% Subsidiary 2021 Senior Notes	—		—			—		688		22			710
Long-term debt, net of current portion	$	2,715	$	(48	)	$	2,667	$	3,165	$	(38	)	$	3,127

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Pension and Post-Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs [Table Text Block]



	Three Months Ended September 30,										Nine Months Ended September 30,
	2018					2017					2018					2017
	U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans		U.S. Plans			Non-U.S. Plans
Service cost	$	1		$	—	$	2		$	—	$	2		$	1	$	4		$	1
Expected administrative expenses	1			—		—			—		2			—		—			—
Interest cost	6			1		6			1		18			2		19			2
Expected return on plan assets	(10		)	—		(10		)	—		(32		)	—		(30		)	—
Amortization of net loss	—			—		—			—		—			—		1			—
Settlement gain	(14		)	—		—			—		(14		)	—		—			—
Net periodic benefit cost (income)	$	(16	)	$	1	$	(2	)	$	1	$	(24	)	$	3	$	(6	)	$	3

Accumulated Other Comprehensive Income (Loss) (Tables)

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]



Details about Accumulated Other Comprehensive Income (Loss) Components	Location of Reclassification (Income (Expense)) in Consolidated Statements of Operations	Three Months Ended September 30,						Nine Months Ended September 30,
		2018			2017			2018			2017
Amortization of pension and other post-retirement net loss	(1)	$	—		$	(1	)	$	—		$	(2	)
Pension settlement gain	(1)	14			—			14			—
Income tax provision on pension and other post-retirement benefits liability	Benefits from (provision for) income taxes	(3		)	1			(3		)	1
Total reclassifications for the period		$	11		$	—		$	11		$	(1	)

_____________


(1)	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost and reflected in other income, net in the consolidated statements of operations. See Note 7 for additional information on the pension settlement gain.

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

Changes in accumulated other comprehensive income (loss) by component for the nine months ended September 30, 2018 and 2017 were as follows:



	Benefits Liability, Net of Tax			Cumulative Foreign Currency Exchange, Net of Tax			Total
Balances at December 31, 2016	$	29		$	(150	)	$	(121	)
Other comprehensive income before reclassifications	—			107			107
Amounts reclassified from accumulated other comprehensive income (loss)	1			—			1
Net other comprehensive income attributable to Westlake Chemical Corporation	1			107			108
Balances at September 30, 2017	$	30		$	(43	)	$	(13	)

Balances at December 31, 2017	$	43		$	(36	)	$	7
Other comprehensive income (loss) before reclassifications	20			(40		)	(20		)
Amounts reclassified from accumulated other comprehensive income (loss)	(11		)	—			(11		)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	9			(40		)	(31		)
Balances at September 30, 2018	$	52		$	(76	)	$	(24	)

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Summary Of Carrying And Fair Values Of Long-Term Debt



	September 30, 2018				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value
3.60% 2022 Senior Notes	$	249	$	246	$	249	$	255
3.60% 2026 Senior Notes	741		704		740		757
Loan related to tax-exempt waste disposal revenue bonds due 2027	11		11		11		11
6 ½% 2029 GO Zone Senior Notes	99		108		99		111
6 ½% 2035 GO Zone Senior Notes	88		96		88		99
6 ½% 2035 IKE Zone Senior Notes	65		70		65		74
5.0% 2046 Senior Notes	675		687		675		787
4.375% 2047 Senior Notes	491		446		491		518
3.50% 2032 GO Zone Refunding Senior Notes	248		241		248		256
4.625% Westlake 2021 Senior Notes	—		—		645		639
4.625% Subsidiary 2021 Senior Notes	—		—		65		65
4.875% Westlake 2023 Senior Notes	—		—		445		449
4.875% Subsidiary 2023 Senior Notes	—		—		16		16

Earnings and Dividends per Share (Tables)

9 Months Ended

Sep. 30, 2018

Earnings Per Share [Abstract]

Schedule Of Net Income Attributable To Common Stockholders

Diluted earnings per share includes the effect of certain stock options.



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Net income attributable to Westlake Chemical Corporation	$	308		$	211		$	873		$	502
Less:
Net income attributable to participating securities	(1		)	(1		)	(4		)	(3		)
Net income attributable to common shareholders	$	307		$	210		$	869		$	499

Reconciliation Of Denominator For Basic And Diluted Earnings Per Share

The following table reconciles the denominator for the basic and diluted earnings per share computations shown in the consolidated statements of operations:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Weighted average common shares—basic	129,427,328		129,069,186		129,512,097		129,033,597
Plus incremental shares from:
Assumed exercise of options	624,964		819,782		671,104		756,368
Weighted average common shares—diluted	130,052,292		129,888,968		130,183,201		129,789,965

Earnings per common share attributable to Westlake Chemical Corporation:
Basic	$	2.36	$	1.62	$	6.70	$	3.87
Diluted	$	2.35	$	1.61	$	6.67	$	3.85

Dividends Per Share

Dividends per Share

Dividends per common share for the three months ended September 30, 2018 and 2017 and for the nine months ended September 30, 2018 and 2017 were as follows:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Dividends per common share	$	0.2500	$	0.2100	$	0.6700	$	0.5912

Segment Information (Tables)

9 Months Ended

Sep. 30, 2018

Segment Reporting [Abstract]

Segment Reporting Information



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Net external sales
Olefins
Polyethylene	$	396		$	377		$	1,152		$	1,121
Styrene, feedstock and other	145			125			374			413
Total Olefins	541			502			1,526			1,534
Vinyls
PVC, caustic soda and other	1,372			1,253			4,126			3,541
Building products	342			354			988			956
Total Vinyls	1,714			1,607			5,114			4,497
	$	2,255		$	2,109		$	6,640		$	6,031

Intersegment sales
Olefins	$	136		$	107		$	368		$	291
Vinyls	—			1			1			1
	$	136		$	108		$	369		$	292

Income (loss) from operations
Olefins	$	162		$	166		$	483		$	489
Vinyls	251			214			788			425
Corporate and other	(17		)	(16		)	(70		)	(52		)
	$	396		$	364		$	1,201		$	862

Depreciation and amortization
Olefins	$	35		$	35		$	102		$	111
Vinyls	124			118			362			332
Corporate and other	2			1			9			6
	$	161		$	154		$	473		$	449

Other income, net
Olefins	$	1		$	—		$	4		$	2
Vinyls	16			1			32			7
Corporate and other	6			3			17			4
	$	23		$	4		$	53		$	13

Provision for (benefit from) income taxes
Olefins	$	34		$	58		$	107		$	152
Vinyls	44			61			174			115
Corporate and other	(5		)	(10		)	(26		)	(34		)
	$	73		$	109		$	255		$	233



	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Capital expenditures
Olefins	$	33	$	21	$	81	$	70
Vinyls	162		108		420		330
Corporate and other	—		4		6		14
	$	195	$	133	$	507	$	414

Reconciliation Of Total Segment Income From Operations To Consolidated Income Before Income Taxes

A reconciliation of total segment income from operations to consolidated income before income taxes is as follows:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2018			2017			2018			2017
Income from operations	$	396		$	364		$	1,201		$	862
Interest expense	(28		)	(40		)	(96		)	(119		)
Other income, net	23			4			53			13
Income before income taxes	$	391		$	328		$	1,158		$	756

Total Assets



	September 30, 2018		December 31, 2017
Total assets
Olefins	$	2,074	$	2,006
Vinyls	8,953		8,853
Corporate and other	694		1,217
	$	11,721	$	12,076

Westlake Chemical Partners LP (Tables)

9 Months Ended

Sep. 30, 2018

Partners' Capital [Abstract]

Schedule of Incentive Distributions Made to Managing Members or General Partners by Distribution [Table Text Block]



	Marginal Percentage Interest in Distributions
Total Quarterly Distribution Per Unit	Unitholders		IDR Holders
Above $1.2938 up to $1.4063	85.0	%	15.0	%
Above $1.4063 up to $1.6875	75.0	%	25.0	%
Above $1.6875	50.0	%	50.0	%



	Marginal Percentage Interest in Distributions
Total Quarterly Distribution Per Unit	Unitholders		IDR Holders
Above $0.3163 up to $0.3438	85.0	%	15.0	%
Above $0.3438 up to $0.4125	75.0	%	25.0	%
Above $0.4125	50.0	%	50.0	%

Basis of Financial Statements Adoption Adjustments (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2016
Item Effected [Line Items]
Net Cash Provided by (Used in) Financing Activities	$ (1,331)	$ (460)
Accounting Standards Update 2016-18 [Member]
Item Effected [Line Items]
Net Cash Provided by (Used in) Financing Activities		(306)
Restricted Cash		$ 32	$ 186

Financial Instruments (Cash Equivalent) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Debt Securities, Held-to-maturity	$ 355	$ 644

Financial Instruments (Restricted Cash Equivalents) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Restricted Cash and Cash Equivalents	$ 23	$ 23

Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts Receivable, Net [Abstract]
Trade customers	$ 1,171	$ 974
Affiliates	11	9
Allowance for doubtful accounts	(24)	(22)
Accounts receivable from trade customers, net	1,158	961
Federal and state taxes	55	7
Other	28	33
Accounts receivable, net	$ 1,241	$ 1,001

Inventories (Inventories) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Finished products	$ 566	$ 549
Feedstock, additives, chemicals and other raw materials	221	221
Materials and supplies	152	130
Inventories	$ 939	$ 900

Goodwill (Details) - USD ($) $ in Millions	9 Months Ended
Goodwill (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill	$ 1,008	$ 1,012
Effects of changes in foreign exchange rates	(4)
Olefins [Member]
Goodwill [Line Items]
Goodwill	30	30
Effects of changes in foreign exchange rates	0
Vinyls [Member]
Goodwill [Line Items]
Goodwill	978	$ 982
Effects of changes in foreign exchange rates	$ (4)

Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal Amount	$ 2,715	$ 3,853
Unamortized Premium (Discount) and Debt Issuance Costs	(48)	(16)
Net, Long-term Debt	2,667	3,837
Long-term Debt, Current Maturities	0	710
Long-term Debt, Gross Excluding Current Maturities	2,715	3,165
Debt Instrument, Unamortized Premium (Discount) and Debt Issuance Cost, Net, Excluding Current Maturities	(48)	(38)
Long-term Debt, Excluding Current Maturities	$ 2,667	3,127
Senior Notes [Member] \| 3.60% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2022
Stated interest rate (percent)	3.60%
Principal Amount	$ 250	250
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 249	249
Senior Notes [Member] \| 3.6% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2026
Stated interest rate (percent)	3.60%
Principal Amount	$ 750	750
Unamortized Premium (Discount) and Debt Issuance Costs	(9)	(10)
Net, Long-term Debt	$ 741	740
Senior Notes [Member] \| Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2027
Principal Amount	$ 11	11
Unamortized Premium (Discount) and Debt Issuance Costs	0	0
Net, Long-term Debt	$ 11	11
Senior Notes [Member] \| 6 1/2% Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2029
Stated interest rate (percent)	6.50%
Principal Amount	$ 100	100
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 99	99
Senior Notes [Member] \| 2035 GO Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 89	89
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 88	88
Senior Notes [Member] \| 2035 IKE Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 65	65
Unamortized Premium (Discount) and Debt Issuance Costs	0	0
Net, Long-term Debt	$ 65	65
Senior Notes [Member] \| 5% Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2046
Stated interest rate (percent)	5.00%
Principal Amount	$ 700	700
Unamortized Premium (Discount) and Debt Issuance Costs	(25)	(25)
Net, Long-term Debt	$ 675	675
Senior Notes [Member] \| 4.375% Senior Notes Due 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2047
Stated interest rate (percent)	4.375%
Principal Amount	$ 500	500
Unamortized Premium (Discount) and Debt Issuance Costs	(9)	(9)
Net, Long-term Debt	$ 491	491
Senior Notes [Member] \| 3.50% Senior Notes Due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2032
Stated interest rate (percent)	3.50%
Principal Amount	$ 250	250
Unamortized Premium (Discount) and Debt Issuance Costs	(2)	(2)
Net, Long-term Debt	$ 248	248
Senior Notes [Member] \| 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2021
Stated interest rate (percent)	4.625%
Principal Amount	$ 0	625
Unamortized Premium (Discount) and Debt Issuance Costs	0	20
Net, Long-term Debt	$ 0	645
Senior Notes [Member] \| 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2021
Stated interest rate (percent)	4.625%
Principal Amount	$ 0	63
Unamortized Premium (Discount) and Debt Issuance Costs	0	2
Net, Long-term Debt	$ 0	65
Senior Notes [Member] \| 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2023
Stated interest rate (percent)	4.875%
Principal Amount	$ 0	434
Unamortized Premium (Discount) and Debt Issuance Costs	0	11
Net, Long-term Debt	$ 0	445
Senior Notes [Member] \| 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2023
Stated interest rate (percent)	4.875%
Principal Amount	$ 0	16
Unamortized Premium (Discount) and Debt Issuance Costs	0	0
Net, Long-term Debt	0	16
Senior Notes [Member] \| 4.625% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-Term Debt, Gross, Current Maturities	0	688
Debt Instrument, Unamortized Premium (Discount) and debt issuance cost, net, Current Maturities	0	22
Long-term Debt, Current Maturities	$ 0	$ 710

Long-Term Debt (New Credit Agreement) (Details) - USD ($) $ in Millions	Jul. 24, 2018	Sep. 30, 2018
New Credit Agreement [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Line Of Credit Facility Permitted Increase	$ 25
New Credit Agreement [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Line Of Credit Facility Permitted Increase	500
New Credit Agreement [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity		$ 996
New Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,000
Line of Credit Facility, Fair Value of Amount Outstanding		0
Letters of Credit Outstanding, Amount		4
New Credit Agreement [Member] \| Letter of Credit [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	150
New Credit Agreement [Member] \| Swingline Loan [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 50
New Credit Agreement [Member] \| Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.00%
New Credit Agreement [Member] \| Alternate Base Rate [Domain] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.75%
New Credit Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
New Credit Agreement [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Credit Agreement [Member] \| Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,000

Long-Term Debt (Senior Notes Due 2021) (Details) - 2021 Notes [Member] - USD ($) $ in Millions		9 Months Ended
	Feb. 15, 2018	Sep. 30, 2018
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.313%
Gain on debt redemption		$ 6

Long-Term Debt (Senior Notes Due 2023) (Details)	May 15, 2018
2023 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage	102.438%

Long-Term Debt (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Unamortized Debt Issuance Cost	$ 26	$ 26

Pension and Post-Retirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 14	$ 0	$ 14	$ 0
Pension Plan [Member] \| Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	1	2	2	4
Defined Benefit Plan, Plan Assets, Administration Expense	1	0	2	0
Defined Benefit Plan, Interest Cost	6	6	18	19
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(10)	(10)	(32)	(30)
Defined Benefit Plan, Amortization of Gain (Loss)	0	0	0	1
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	(14)	0	(14)	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(16)	(2)	(24)	(6)
Pension Plan [Member] \| Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Service Cost	0	0	1	1
Defined Benefit Plan, Plan Assets, Administration Expense	0	0	0	0
Defined Benefit Plan, Interest Cost	1	1	2	2
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	0	0	0	0
Defined Benefit Plan, Amortization of Gain (Loss)	0	0	0	0
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 1	$ 1	$ 3	$ 3

Pension and Post-Retirement Benefits (Details) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 14	$ 0	$ 14	$ 0
Other Comprehensive Income (Loss) [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Net Periodic Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income	$ 26

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity Attributable to Parent	$ 5,602		$ 5,602		$ 4,874
Accumulated other comprehensive income (loss)	(24)	$ (13)	(24)	$ (13)	7	$ (121)
Other comprehensive income (loss)	9	40	(33)	110
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity Attributable to Parent	52	30	52	30	43	29
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			20	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(11)	1
Other comprehensive income (loss)			9	1
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity Attributable to Parent	$ (76)	$ (43)	(76)	(43)	$ (36)	$ (150)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(40)	107
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0	0
Other comprehensive income (loss)			(40)	107
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax			(20)	107
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(11)	1
Other comprehensive income (loss)			$ (31)	$ 108

Accumulated Other Comprehensive Income (Loss) (Reclassification out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement	$ 14	$ 0	$ 14	$ 0
Provision for income taxes	73	109	255	233
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total Reclassifications for the period	11	0	11	(1)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total Reclassifications for the period			11	(1)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	0	(1)	0	(2)
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes	$ (3)	$ 1	$ (3)	$ 1

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 2,667	$ 3,837
3.60% Senior Notes Due 2022 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 249	249
Debt Instrument Maturity	2022
Stated interest rate (percent)	3.60%
3.6% Senior Notes Due 2026 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 741	740
Debt Instrument Maturity	2026
Stated interest rate (percent)	3.60%
Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 11	11
Debt Instrument Maturity	2027
6 1/2% Senior Notes Due 2029 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 99	99
Debt Instrument Maturity	2029
Stated interest rate (percent)	6.50%
2035 GO Zone 6 1/2% Notes [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 88	88
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
2035 IKE Zone 6 1/2% Notes [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 65	65
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
5% Senior Notes Due 2046 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 675	675
Debt Instrument Maturity	2046
Stated interest rate (percent)	5.00%
4.375% Senior Notes Due 2047 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 491	491
Debt Instrument Maturity	2047
Stated interest rate (percent)	4.375%
3.50% Senior Notes Due 2032 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 248	248
Debt Instrument Maturity	2032
Stated interest rate (percent)	3.50%
4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 0	645
Debt Instrument Maturity	2021
Stated interest rate (percent)	4.625%
4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 0	65
Debt Instrument Maturity	2021
Stated interest rate (percent)	4.625%
4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 0	445
Debt Instrument Maturity	2023
Stated interest rate (percent)	4.875%
4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 0	16
Debt Instrument Maturity	2023
Stated interest rate (percent)	4.875%
Fair Value [Member] \| 3.60% Senior Notes Due 2022 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 246	255
Fair Value [Member] \| 3.6% Senior Notes Due 2026 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	704	757
Fair Value [Member] \| Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	11	11
Fair Value [Member] \| 6 1/2% Senior Notes Due 2029 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	108	111
Fair Value [Member] \| 2035 GO Zone 6 1/2% Notes [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	96	99
Fair Value [Member] \| 2035 IKE Zone 6 1/2% Notes [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	70	74
Fair Value [Member] \| 5% Senior Notes Due 2046 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	687	787
Fair Value [Member] \| 4.375% Senior Notes Due 2047 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	446	518
Fair Value [Member] \| 3.50% Senior Notes Due 2032 [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	241	256
Fair Value [Member] \| 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	639
Fair Value [Member] \| 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	65
Fair Value [Member] \| 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	449
Fair Value [Member] \| 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member] \| Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 0	$ 16

Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
Income Taxes (Narrative) (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	18.70%	33.10%	22.00%	30.80%
U.S. federal statutory income tax rate	21.00%	35.00%	21.00%	35.00%
Provisional adjustment of income tax benefit					$ 591

Earnings and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 308	$ 211	$ 873	$ 502
Net income attributable to participating securities	(1)	(1)	(4)	(3)
Net income attributable to common shareholders	$ 307	$ 210	$ 869	$ 499

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Earnings and Dividends per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Weighted average common shares—basic	129,427,328	129,069,186	129,512,097	129,033,597
Incremental Shares From Assumed exercise of options	624,964	819,782	671,104	756,368
Weighted average common shares-diluted	130,052,292	129,888,968	130,183,201	129,789,965
Earnings per share attributable to Westlake Chemical Corporation: Basic	$ 2.36	$ 1.62	$ 6.70	$ 3.87
Earnings per share attributable to Westlake Chemical Corporation: Diluted	$ 2.35	$ 1.61	$ 6.67	$ 3.85

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=109256448&loc=d3e4984-109258

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1252-109256

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(23))
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22694-107794

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109260490&loc=d3e1337-109256

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(21))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109260490&loc=SL5780133-109256

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(19))
-URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263

+ Details

Earnings and Dividends per Share (Additional Information) (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Number of options excluded from computation of diluted earnings per share	172,194	335,276	143,439	291,888

Earnings and Dividends per Share Dividends Per Share (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Dividends per common share (in usd per share)	$ 0.2500	$ 0.2100	$ 0.6700	$ 0.5912

Supplemental Information ( Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accrued Liabilities [Abstract]
Accrued liabilities	$ 675		$ 675		$ 657
Accrued Rebates, Current	112		112		108
Due to Affiliate, Current	45		45		$ 37
Increase (Decrease) in Capital Expenditure Accrual			(8)	$ 8
One-time settlement gain		$ 2	23	6
Income (Loss) from Subsidiaries, Net of Tax	5	4	17	11
Interest Income, Other	4	$ 1	13	$ 2
2021 Notes [Member]
Accrued Liabilities [Abstract]
Gain on debt redemption			$ 6
Other Income [Member]
Accrued Liabilities [Abstract]
Defined Benefit Plan, Net Periodic Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income	$ 16

Commitments and Contingencies (Additional Information) (Detail) - USD ($) $ in Millions		1 Months Ended	9 Months Ended
	Jun. 18, 2018	May 31, 2017	Sep. 30, 2018	Dec. 31, 2017
Environmental Loss Contingencies [Line Items]
Environmental Loss contingency accrual			$ 57	$ 49
Site Contingency, Percentage of Cost Potentially of Other Responsible Parties [Line Items]			100.00%
PolyOne [Member] \| Pending Litigation [Member]
Environmental Loss Contingencies [Line Items]
Maximum Expected Damages		$ 17
Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss			$ 55
Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss			110
Environmental Protection Agency [Member] \| Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Remediation Expense			200
Environmental Protection Agency [Member] \| Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Remediation Expense			250
Environmental Protection Agency [Member] \| Operation and Maintenance [Member]
Environmental Loss Contingencies [Line Items]
Environmental Remediation Expense	$ 107
Environmental Protection Agency [Member] \| Operation and Maintenance [Member] \| Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost			1
Environmental Protection Agency [Member] \| Operation and Maintenance [Member] \| Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost			3
Affiliated Entity [Member] \| LACC [Member]
Environmental Loss Contingencies [Line Items]
Maximum Capital Commitment			$ 225
Ownership interest (in percent)			10.00%
Funding to related parties			$ 178

Segment Information (Additional Information) (Detail)	9 Months Ended
Segment Information (Additional Information) (Detail)	Sep. 30, 2018 Segment
Segment Reporting [Abstract]
Number of segments	2

Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 2,255	$ 2,109	$ 6,640	$ 6,031
Income (loss) from operations	396	364	1,201	862
Depreciation and amortization	161	154	473	449
Other income (expense), net	23	4	53	13
Provision for (benefit from) income taxes	73	109	255	233
Additions to property, plant and equipment	195	133	507	414
Operating Segments [Member] \| Olefins [Member]
Segment Reporting Information [Line Items]
Revenues	541	502	1,526	1,534
Income (loss) from operations	162	166	483	489
Depreciation and amortization	35	35	102	111
Other income (expense), net	1	0	4	2
Provision for (benefit from) income taxes	34	58	107	152
Additions to property, plant and equipment	33	21	81	70
Operating Segments [Member] \| Vinyls [Member]
Segment Reporting Information [Line Items]
Revenues	1,714	1,607	5,114	4,497
Income (loss) from operations	251	214	788	425
Depreciation and amortization	124	118	362	332
Other income (expense), net	16	1	32	7
Provision for (benefit from) income taxes	44	61	174	115
Additions to property, plant and equipment	162	108	420	330
Operating Segments [Member] \| Polyethylene [Member] \| Olefins [Member]
Segment Reporting Information [Line Items]
Revenues	396	377	1,152	1,121
Operating Segments [Member] \| Styrene, Feedstock And Other [Member] \| Olefins [Member]
Segment Reporting Information [Line Items]
Revenues	145	125	374	413
Operating Segments [Member] \| PVC, Caustic Soda And Other [Member] \| Vinyls [Member]
Segment Reporting Information [Line Items]
Revenues	1,372	1,253	4,126	3,541
Operating Segments [Member] \| Building Products [Member] \| Vinyls [Member]
Segment Reporting Information [Line Items]
Revenues	342	354	988	956
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(17)	(16)	(70)	(52)
Depreciation and amortization	2	1	9	6
Other income (expense), net	6	3	17	4
Provision for (benefit from) income taxes	(5)	(10)	(26)	(34)
Additions to property, plant and equipment	0	4	6	14
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Revenues	136	108	369	292
Intersegment sales [Member] \| Olefins [Member]
Segment Reporting Information [Line Items]
Revenues	136	107	368	291
Intersegment sales [Member] \| Vinyls [Member]
Segment Reporting Information [Line Items]
Revenues	$ 0	$ 1	$ 1	$ 1

Segment Information (Reconciliation of Total Segment Income from Operations to Consolidated Income before Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting [Abstract]
Income from operations	$ 396	$ 364	$ 1,201	$ 862
Interest expense	(28)	(40)	(96)	(119)
Other income (expense), net	23	4	53	13
Income before income taxes	$ 391	$ 328	$ 1,158	$ 756

Segment Information (Total Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 11,721	$ 12,076
Operating Segments [Member] \| Olefins [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,074	2,006
Operating Segments [Member] \| Vinyls [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	8,953	8,853
Corporate and other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 694	$ 1,217

Westlake Chemical Partners LP (Details) - $ / shares		3 Months Ended	9 Months Ended
Westlake Chemical Partners LP (Details) - $ / shares	Jul. 27, 2018	Sep. 30, 2018	Sep. 30, 2018
Subsidiary of Common Parent [Member] \| Westlake Chemical OpCo LP [Member] \| Limited Partner [Member] \| IPO [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest			81.70%
Subsidiary of Common Parent [Member] \| Westlake Chemical Partners LP [Member] \| Limited Partner [Member] \| IPO [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest			43.80%
Cash Distribution [Member]
Class of Stock [Line Items]
Incentive Distribution, Distribution Per Unit	$ 1.2938	$ 1.2938
Unit Holders [Member] \| Cash Distribution, Tranche One [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	85.00%	85.00%
Unit Holders [Member] \| Cash Distribution, Tranche Two [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	75.00%	75.00%
Unit Holders [Member] \| Cash Distribution, Tranche Three [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	50.00%	50.00%
IDR Holders [Member] \| Cash Distribution, Tranche One [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	15.00%	15.00%
IDR Holders [Member] \| Cash Distribution, Tranche Two [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	25.00%	25.00%
IDR Holders [Member] \| Cash Distribution, Tranche Three [Member]
Class of Stock [Line Items]
Maximum Percentage Of Income Distribution	50.00%	50.00%
Minimum [Member] \| Cash Distribution, Tranche One [Member]
Class of Stock [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders	$ 1.2938	$ 0.3163
Minimum [Member] \| Cash Distribution, Tranche Two [Member]
Class of Stock [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders	1.4063	0.3438
Minimum [Member] \| Cash Distribution, Tranche Three [Member]
Class of Stock [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders	1.6875	0.4125
Maximum [Member] \| Cash Distribution, Tranche One [Member]
Class of Stock [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders	1.4063	0.3438
Maximum [Member] \| Cash Distribution, Tranche Two [Member]
Class of Stock [Line Items]
Incentive Distribution Rights, Target Distribution Per Unit Requiring Marginal Percentage Distribution to IDR Holders	$ 1.6875	$ 0.4125

Subsequent Events Subsequent Events (Details) $ in Millions	Oct. 04, 2018 USD ($)
Subsequent Event [Member]
Subsequent Event [Line Items]
Partners' Units, Maximum Aggregate Offering Amount, ATM	$ 50