Goodwill and Intangible Assets Disclosure [Abstract] Goodwill, Intangibles and Other Assets Goodwill and Intangible Assets Disclosure [Text Block] Defined Benefit Plan [Abstract] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Defined Benefit Plans [Member] Defined Benefit Plans [Member] Defined Benefit Plans [Member] Other Postretirement Plan Benefits [Member] Other Postretirement Benefits Plan [Member] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block] Schedule of Amounts Recognized in Balance Sheet Schedule of Amounts Recognized in Balance Sheet [Table Text Block] Schedule of Amounts Recognized in Other Comprehensive Income (Loss) Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Schedule Of Accumulated Benefit Obligations In Excess Of Plan Assets Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block] Schedule Of Net Benefit Costs And Amounts Recognized In Other Comprehensive Income Schedule Of Net Benefit Costs And Amounts Recognized In Other Comprehensive Income Loss [Table Text Block] Tabular disclosure of 1) the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments, and 2) the net gain (loss) and net prior service cost or credit recognized in other comprehensive income (loss) for the period for pension plans and/or other employee benefit plans, and reclassification adjustments of other comprehensive income (loss) for the period, as those amounts, including amortization of the net transition asset or obligation, are recognized as components of net periodic benefit cost. Schedule Of Weighted Average Assumptions Used Schedule of Assumptions Used [Table Text Block] Schedule Of Fair Value Of Pension Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Schedule of Multi-employer Plans Schedule of Multiemployer Plans [Table Text Block] Schedule Of Estimated Future Benefit Payments Schedule of Expected Benefit Payments [Table Text Block] Equity [Abstract] Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Westlake Chemical Partners LP Partners' Capital Notes Disclosure [Text Block] Income Tax Disclosure [Abstract] Domestic Income (Loss) from Continuing Operations before Income Taxes, Domestic Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Other Comprehensive Income (Loss) [Member] AOCI Attributable to Parent [Member] Benefits Liability, Net of Tax Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Cumulative Foreign Currency Exchange Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Net Unrealized Holding Gains on Investments, Net of Tax Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Total equity, beginning balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Other comprehensive income (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from accumulated other comprehensive income (loss) Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive income attributable to Westlake Chemical Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Total equity, ending balance Fair Value Disclosures [Abstract] Schedule Of Carrying And Fair Values Of Long-Term Debt Fair Value, by Balance Sheet Grouping [Table Text Block] Condensed Financial Information of Parent Company Only Disclosure [Abstract] Guarantor Disclosures Condensed Financial Information of Parent Company Only Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Regulatory Agency [Axis] Regulatory Agency [Axis] Regulatory Agency [Domain] Regulatory Agency [Domain] Environmental Protection Agency [Member] Environmental Protection Agency [Member] Environmental Protection Agency [Member] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Domain] Environmental Remediation Contingency [Domain] Operation and Maintenance [Member] Operation and Maintenance [Member] Operation and Maintenance [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] PolyOne [Member] PolyOne [Member] PolyOne [Member] Litigation Status [Axis] Litigation Status [Axis] Litigation Status [Domain] Litigation Status [Domain] Pending Litigation [Member] Pending Litigation [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Environmental contingency accrual Loss Contingency Accrual Environmental Remediation Expense Estimated Environmental Remediation Expense Environmental Exit Costs, Anticipated Cost Environmental Exit Costs, Anticipated Cost Loss Contingency, Damages Sought, Value Loss Contingency, Damages Sought, Value Gain Contingency, Unrecorded Amount Gain Contingency, Unrecorded Amount Reasonably possible additional loss - Environmental Environmental Exit Costs, Reasonably Possible Additional Loss Earnings Per Share [Abstract] Schedule Of Net Income Attributable To Common Stockholders Schedule Of Net Income Loss Attributable To Common Stockholders [Table Text Block] Schedule of net income (loss) attributable to common stockholders [Table Text Block] Reconciliation Of Denominator For Basic And Diluted Earnings (Loss) Per Share Schedule of Weighted Average Number of Shares [Table Text Block] Long-term Debt, Unclassified [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes [Member] Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 6.5% 2035 IKE Zone Senior Notes [Member] Ike Zone Six Point Five Percent Tax Exempt Revenue Bonds Due Twenty Thirty Five [Member] IKE Zone six point five percent tax-exempt revenue bonds due twenty thirty five [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term Debt, Gross Long-term Debt, Gross Credit Agreement [Abstract] Credit Agreement [Abstract] Line of Credit Facility [Table] Line of Credit Facility [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR [Member] London Interbank Offered Rate (LIBOR) [Member] Alternate Base Rate [Domain] Alternate Base Rate [Domain] Alternate Base Rate [Domain] Senior Secured Revolving Credit Facility [Member] Line of Credit [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility [Member] Revolving Credit Facility [Member] Term Loan [Line Items] Line of Credit Facility [Line Items] Line of Credit Facility, Maximum Borrowing Capacity Line of Credit Facility, Maximum Borrowing Capacity Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Line of Credit Facility, Fair Value of Amount Outstanding Line of Credit Facility, Fair Value of Amount Outstanding Letters of Credit Outstanding, Amount Letters of Credit Outstanding, Amount Line of Credit Facility, Remaining Borrowing Capacity Line of Credit Facility, Remaining Borrowing Capacity Quarterly Financial Information Disclosure [Abstract] Summary Of Quarterly Financial Information Quarterly Financial Information [Table Text Block] Debt Disclosure [Abstract] Long-Term Debt Long-term Debt [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment by Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Buildings And Improvements [Member] Building and Building Improvements [Member] Plant And Equipment [Member] Plant And Equipment [Member] Plant And Equipment [Member] Ethylene Pipeline [Member] Ethylene Pipeline [Member] Ethylene Pipeline [Member] Other [Member] Other Capitalized Property Plant and Equipment [Member] Property, Plant and Equipment [Line Items] Property, plant and equipment, useful life, minimum (in years) Property, Plant and Equipment, Useful Life Term Loan Short-term Debt [Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Related Party Transactions [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Cypress Interstate Pipeline L.L.C [Member] Cypress Interstate Pipeline L.L.C [Member] Cypress Interstate Pipeline L.L.C [Member] EPS Ethylene Pipeline Süd GmbH & Co. KG [Member] EPS Ethylene Pipeline Süd GmbH & Co. KG [Member] EPS Ethylene Pipeline Süd GmbH & Co. KG [Member] InfraServ Knapsack GmbH & Co. KG [Member] InfraServ Knapsack GmbH & Co. KG [Member] InfraServ Knapsack GmbH & Co. KG [Member] InfraServ Gendorf GmbH & Co. KG [Member] InfraServ Gendorf GmbH & Co. KG [Member] InfraServ Gendorf GmbH & Co. KG [Member] InfraServ Knapsack & Gendorf GmbH & Co. KG [Member] InfraServ Knapsack & Gendorf GmbH & Co. KG [Member] InfraServ Knapsack & Gendorf GmbH & Co. KG [Member] Shriram Axiall Private Limited [Member] Shriram Axiall Private Limited [Member] Shriram Axiall Private Limited [Member] RS Cogen LLC [Member] RS Cogen LLC [Member] RS Cogen LLC [Member] Vinyl Solutions, LLC [Member] Vinyl Solutions, LLC [Member] Vinyl Solutions, LLC [Member] LACC [Member] LACC [Member] LACC [Member] American Air Liquide Holdings [Member] American Air Liquide Holdings [Member] American Air Liquide Holdings [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Pipeline Fees For Transport Of Natural Gas Liquid Feedstocks [Member] Pipeline Fees For Transport Of Natural Gas Liquid Feedstocks [Member] Pipeline Fees For Transport Of Natural Gas Liquid Feedstocks [Member] Electricity And Technical Services [Member] Electricity And Technical Services [Member] Electricity and Technical Services [Member] Pipeline Fees For Transport Of Ethylene Feedstocks [Member] Pipeline Fees For Transport Of Ethylene Feedstocks [Member] Pipeline Fees For Transport Of Ethylene Feedstocks [Member] Equity Method Investee, Name [Axis] Investment, Name [Axis] Equity Method Investee, Name [Domain] Investment, Name [Domain] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Affiliates [Member] Affiliated Entity [Member] Corporate Joint Venture [Member] Corporate Joint Venture [Member] American Air Liquide Holdings, Inc. [Member] Director [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Incurred and paid lease payments Office Lease Expense Lease expense incurred for office space. Ownership interest (in percent) Equity Method Investment, Ownership Percentage Investments in joint ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Purchases from related parties Related Party Transaction, Purchases from Related Party Accounts payable due to affiliate Due to Affiliate Ownership percentage by parent Noncontrolling Interest, Ownership Percentage by Parent Sales to related parties Revenue from Related Parties Related party receivable Accounts Receivable, Related Parties, Current Plant capacity (in T) Related Party Transaction, Plant Capacity Related Party Transaction, Plant Capacity Maximum Capital Commitment Investment Company, Financial Commitment to Investee, Future Amount Optional ownership percentage Equity Method Investment, Ownership Percentage, Option Equity Method Investment, Ownership Percentage, Option Funding to related parties Payments to Fund Long-term Loans to Related Parties Accounts payable due to related parties Accounts Payable, Related Parties Dividends received from equity method investments Proceeds from Equity Method Investment, Distribution Purchases and lease expense to related parties Purchases And Lease Expense Payments made for purchases and lease expenses. Share-based Compensation [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Axiall Corporation [Member] Axiall Corporation [Member] Axiall Corporation [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Schedule Of Option Activity And Changes Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable [Table Text Block] Schedule Of Range Of Exercise Prices For Outstanding Options Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block] Schedule Of Weighted Average Value And Assumptions For Fair Value Of Options Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule Of Non-Vested Restricted Stock Award Activity And Changes Schedule of Nonvested Share Activity [Table Text Block] Property, Plant and Equipment, Net [Abstract] Schedule Of Property, Plant And Equipment Property, Plant and Equipment [Table Text Block] Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Suzhou Huasu Plastics Company Ltd [Member] Suzhou Huasu Plastics Company Ltd [Member] Suzhou Huasu Plastics Company, Ltd. Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] PVC Resin [Member] PVC Resin [Member] PVC Resin [Member] PVC Film [Member] PVC Film [Member] PVC Film Business Acquisition [Line Items] Business Acquisition [Line Items] Equity interest in acquiree held prior to combination, shares Business Combination, Equity Interest in Acquiree Held Prior to Combination, Shares Business Combination, Equity Interest in Acquiree Held Prior to Combination, Shares Offer price per share (usd per share) Business Acquisition, Share Price Purchase price Business Combination, Consideration Transferred Transaction and integration-related costs Business Combination, Integration Related Costs Professional fees Business Acquisition, Transaction Costs Share-based awards, Retention & Severance Severance Costs Contribution to net sales Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Contribution to net loss Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Goodwill Goodwill Percentage of interests acquired Business Acquisition, Percentage of Voting Interests Acquired Percentage of interest held after acquisition Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage Combined annual capacity (in lb's) Business Combination, Annual Production Capacity Business Combination, Annual Production Capacity Ownership Percentage held prior to acquisition Remeasurement gain (loss) Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net Fair value of consideration transferred-cash Payments to Acquire Businesses, Gross Bargain purchase gain on acquisition Business Combination, Bargain Purchase, Gain Recognized, Amount Description Of Business And Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Retirement Benefits [Abstract] Defined Contribution Plan [Table] Defined Contribution Plan [Table] Defined Contribution Retirement Plan [Member] Defined Contribution Retirement Plan [Member] Defined Contribution Retirement Plan [Member] Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Domain] Retirement Plan Sponsor Location [Domain] Domestic Plan [Member] Domestic Plan [Member] Foreign Plan [Member] Foreign Plan [Member] Defined Contribution Plan [Line Items] Defined Contribution Plan Disclosure [Line Items] Maximum employee contribution as a percentage of annual compensation Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Employer contributions to plans Defined Contribution Plan, Employer Discretionary Contribution Amount Number of subsidiaries company provides a defined contribution plan Number of Subsidiaries Company Provides A Defined Contribution Plan Number of Subsidiaries Company Provides A Defined Contribution Plan Length of service required to be eligible for annual retirement contributions (in years) Eligibility Requirements Length Of Service Required For Annual Retirement Contribution Eligibility requirements, length of service required for annual retirement contribution Employer Contributions to Plan Defined Contribution Plan, Cost Income Statement [Abstract] Net sales Revenue, Net Cost of sales Cost of Goods Sold Gross profit Gross Profit Selling, general and administrative expenses Selling, General and Administrative Expense Amortization of intangibles Amortization of Intangible Assets Income from operations Operating Income (Loss) Other income (expense) Nonoperating Income (Expense) [Abstract] Interest expense Interest Expense Other income, net Nonoperating Income (Expense) Provision for (benefit from) income taxes Income Tax Expense (Benefit) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Net income attributable to Westlake Chemical Corporation Net Income (Loss) Attributable to Parent Earnings per common share attributable to Westlake Chemical Corporation: Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Weighted average shares outstanding Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Dividends per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Options excluded from computation of earnings per share, shares Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule Of Other Assets [Table] Schedule Of Other Assets [Table] Schedule Of Other Assets [Table] Segments [Axis] Segments [Axis] Segment [Domain] Segments [Domain] Olefins [Member] Olefins [Member] Olefins [Member] Vinyls [Member] Vinyls [Member] Vinyls [Member] Valuation Technique [Axis] Valuation Technique [Axis] Valuation Technique [Domain] Valuation Technique [Domain] Discounted Cash Flow and Market Approach Valuation Technique [Member] Discounted Cash Flow and Market Approach Valuation Technique [Member] Discounted Cash Flow and Market Approach Valuation Technique [Member] Market Approach Valuation Technique [Member] Market Approach Valuation Technique [Member] Other Assets [Line Items] Other Assets [Line Items] Other Assets [Line Items] Number of years forecasted to test for impairment of goodwill Discounted Cash Flow Methodology, Asset Impairment, Number Of Years Forecasted The number of forecast years utilized in developing discounted cash flow projections in determining asset impairment. Discount rate Fair Value Inputs, Discount Rate Statement of Cash Flows [Abstract] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Stock-based compensation expense Share-based Compensation Gains realized on previously held shares of Axiall common stock and from sales of securities Available-for-sale Securities, Gross Realized Gain (Loss) Gain on acquisition, net of loss on the fair value remeasurement of preexisting equity interest Business Combination, Bargain Purchase, Gain Net Business Combination, Bargain Purchase, Gain Recognized, Amount, Including Remeasurement Loss Loss from disposition of property, plant and equipment Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Deferred income taxes Deferred Income Tax Expense (Benefit) Other losses, net Other Operating Activities, Cash Flow Statement Changes in operating assets and liabilities, net of effect of business acquisitions Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts and Other Receivables Inventories Increase (Decrease) in Inventories Prepaid expenses and other current assets Increase (Decrease) In Prepaid Expenses And Other Current Assets Increase (Decrease) In Prepaid Expenses And Other Current Assets Accounts payable Increase (Decrease) in Accounts Payable Accrued liabilities Increase (Decrease) in Accrued Liabilities Other, net Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Acquisition of business, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Additions to property, plant and equipment Payments to Acquire Property, Plant, and Equipment Additions to cost method investment Payments to Acquire Additional Interest in Subsidiaries Proceeds from disposition of equity method investment Proceeds from Sale of Equity Method Investments Proceeds from sales and maturities of securities Proceeds from Sale and Maturity of Marketable Securities Purchase of securities Payments to Acquire Investments Other Payments for (Proceeds from) Other Investing Activities Net cash used for investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Debt issuance costs Payments of Debt Issuance Costs Dividends paid Payments of Ordinary Dividends, Common Stock Distributions to noncontrolling interests Payments to Noncontrolling Interests Proceeds from debt issuance and drawdown of revolver Proceeds from Long-term Lines of Credit Net proceeds from issuance of Westlake Chemical Partners LP common units Proceeds from Issuance of Common Limited Partners Units Proceeds from senior notes issuance Proceeds from Issuance of Long-term Debt Repayment of term loan Repayments of Short-term Debt Restricted cash associated with term loan Increase (Decrease) in Restricted Cash Repayment of revolver Repayments of Lines of Credit Repayment of notes payable Repayments of Notes Payable Repurchase of common stock for treasury Payments for Repurchase of Common Stock Other Proceeds from (Payments for) Other Financing Activities Net cash provided by (used for) financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash and Cash Equivalents Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents at beginning of the year Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of the year Acquisitions Business Combination Disclosure [Text Block] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Pension Plan Benefits [Member] Pension Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Year 1 Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months Year 2 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Year 3 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Year 4 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Year 5 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Years 6 to 10 Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter Provision for federal income tax, at statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount State income tax provision, net of federal income tax effect Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Foreign income tax rate differential Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount Manufacturing deduction Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount Depletion Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depletion, Amount Noncontrolling interests Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Amount Tax on previously held shares of Axiall Corporation and certain other acquisition related items Effective Income Tax Rate Reconciliation, Acquisition of Business, Amount Effective Income Tax Rate Reconciliation, Acquisition of Business, Amount Tax Act related adjustment Income Tax Credits and Adjustments Changes in state apportionment and other state adjustments Effective Income Tax Rate Reconciliation, Tax Settlement, State and Local, Amount Research and development expenditures and adjustments related to prior years' tax returns Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount Other, net Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Provision for (benefit from) income taxes Statement of Financial Position [Abstract] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Common stock, par value per share (in dollars per share) Common Stock, Par or Stated Value Per Share Common Stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, held in treasury Treasury Stock, Shares Current liabilities Liability, Defined Benefit Plan, Current Noncurrent liabilities Liability, Defined Benefit Plan, Noncurrent Net amount recognized Liability, Defined Benefit Plan 3.60% Senior Notes Due 2022 [Member] Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member] Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member] Principal amount Debt Instrument, Unamortized Discount Debt Instrument, Unamortized Discount Minimum Debt Amount Guaranteed By Subsidiaries Minimum Debt Amount Guaranteed By Subsidiaries Minimum Debt Amount Guaranteed By Subsidiaries Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted Stock [Member] Restricted Stock [Member] Restricted Stock Units (RSUs) [Member] Restricted Stock Units (RSUs) [Member] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Number of Shares, Non-vested, beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Number of Shares, Granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Number of Shares, Vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Number of Shares, Forfeited Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Number of Shares, Non-vested, ending balance Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted Average Fair Value, Non-vested, beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Weighted Average Fair Value, Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted Average Fair Value, Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Weighted Average Fair Value, Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Weighted Average Fair Value, Non-vested, ending balance (in dollars per share) Multiplied by number of shares outstanding at acquisition (in thousands of shares) Business Combination, Shares Outstanding Business Combination, Shares Outstanding Fair value of Axiall shares outstanding purchased by the Company Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Axiall debt repaid at acquisition Business Combination, Retirement Of Debt Not Assumed In Acquisition Business Combination, Retirement Of Debt Not Assumed In Acquisition Seller's transaction costs paid by the Company Business Combinations, Sellers Transaction Costs Paid Business Combinations, Sellers Transaction Costs Paid Total fair value of consideration transferred Business Combination, Consideration Transferred, Fair Value Business Combination, Consideration Transferred, Fair Value Fair value of Axiall share-based awards attributed to pre-combination service Business Combination, Fair Value of Share-Based Compensation Awards Acquired Business Combination, Fair Value of Share-Based Compensation Awards Acquired Additional settlement value of shares acquired Business Combination, Settlement Value of Share-Based Compensation Awards Acquired Business Combination, Settlement Value of Share-Based Compensation Awards Acquired Purchase consideration Fair value of previously held equity interest in Axiall Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination Total fair value allocated to net assets acquired Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest Remeasurement gain (loss) Quarterly Financial Information Quarterly Financial Information [Text Block] Investments, Debt and Equity Securities [Abstract] Held-to-maturity Securities Held-to-maturity Securities Restricted cash and cash equivalents Restricted Cash and Cash Equivalents Restricted cash and cash equivalents current Restricted Cash and Cash Equivalents, Current Restricted cash and cash equivalents noncurrent Restricted Cash and Cash Equivalents, Noncurrent Segment Reporting [Abstract] Reconciliation of Assets from Segment to Consolidated [Table] Reconciliation of Assets from Segment to Consolidated [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments [Member] Operating Segments [Member] Corporate, Non-Segment [Member] Corporate, Non-Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Total assets Assets Weighted average common shares—basic Plus incremental shares from: Assumed exercise of options Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants Weighted average common shares—diluted Receivables [Abstract] Trade customers Accounts Receivable, Gross, Current Affiliates Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable, Current Accounts Receivable from trade customers, net Accounts Receivable, Net, Current Federal and state taxes Income Taxes Receivable, Current Other Other Receivables, Net, Current Accounts receivable, net Receivables, Net, Current Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] UNITED STATES UNITED STATES Germany [Member] GERMANY Canada [Member] CANADA Switzerland [Member] SWITZERLAND BRAZIL BRAZIL China [Member] CHINA Italy [Member] ITALY TAIWAN, PROVINCE OF CHINA TAIWAN, PROVINCE OF CHINA Other [Member] Other Foreign Countries [Member] Other Foreign Countries [Member] Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Long-lived assets Property, Plant and Equipment, Net Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Reported Value Measurement [Member] Reported Value Measurement [Member] Estimate of Fair Value Measurement [Member] Estimate of Fair Value Measurement [Member] Revolving Credit Facility [Member] Unsecured Revolving Credit Facility [Member] Unsecured Revolving Credit Facility [Member] Line of Credit [Member] Waste Disposal Revenue Bonds Due 2027 [Member] Waste Disposal Revenue Bonds Due Twenty Twenty Seven [Member] Waste Disposal Revenue Bonds Due Twenty Twenty-Seven [Member] 4.625% Westlake Senior Notes 2021 [Member] Four Point Six Two Five Percent Senior Notes Due Twenty Twenty-One New Westlake Notes [Member] Four Point Six Two Five Percent Senior Notes Due Twenty Twenty-One New Westlake Notes [Member] 4.625% Subsidiary Senior Notes 2021 [Member] Four Point Six Two Five Percent Senior Notes Due Twenty Twenty-One Existing Axiall Notes [Member] Four Point Six Two Five Percent Senior Notes Due 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[Abstract] Document And Entity Information (Abstract) Document Type Amendment Flag Document Period End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Entity Filer Category Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Common Stock, Shares Outstanding Entity Public Float Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Options, Outstanding, beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Options, Granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Options, Exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Options, Cancelled Share-based Compensation Arrangement by Share-based Payment Award, Options, 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dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Weighted Average Exercise Price, Outstanding, ending balance (in dollars per share) Weighted Average Exercise Price, Exercisable, ending balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted Average Remaining Term (Years), Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted Average Remaining Term (Years), Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Aggregate Intrinsic Value, Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate Intrinsic Value, Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Segment and Geographic Information Segment Reporting Disclosure [Text Block] Statement of Comprehensive Income [Abstract] Comprehensive income (loss) including portion attributable to noncontrolling interest, tax Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest Service cost Defined Benefit Plan, Service Costs Paid Defined Benefit Plan, Service Costs Paid Administrative expenses Defined Benefit Plan, Administration Expenses Paid Defined Benefit Plan, Administration Expenses Paid Interest cost Defined Benefit Plan, Interest Cost Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Net amortization Defined Benefit Plan, Other Cost (Credit) Settlement benefits Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Net periodic benefit cost (gain) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Net loss (gain) emerging Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Amortization of net loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Total recognized in OCI Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax Total net periodic benefit cost and OCI Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income (Loss) And Net Periodic Benefit Credit (Cost) The total amount of net periodic benefit cost and the aggregate net gain (loss) recognized in other comprehensive income for the period. Defined Benefit Plan, Expected Prior Service Cost (Credit), Next Fiscal Year Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year Defined Benefit Plan, Expected Gain (Loss), Next Fiscal Year Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year Schedule of Condensed Financial Statements [Table] Condensed Financial Statements [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Westlake Chemical Corporation [Member] Parent Company [Member] 100% Owned Guarantor Subsidiaries [Member] Guarantor Subsidiaries [Member] Non-Guarantor Subsidiaries [Member] Non-Guarantor Subsidiaries [Member] Eliminations [Member] Consolidation, Eliminations [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Cash and cash equivalents Accounts receivable, net Inventories Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Restricted cash Total current assets Assets, Current Property, plant and equipment, net Customer relationships, net Finite-Lived Intangible Assets, Net Other intangible assets, net Other Intangible Assets, Net Other assets, net Deferred Costs and Other Assets Total assets Accounts payable Accounts Payable, Current Accrued liabilities Accrued Liabilities, Current Current portion of long-term debt, net Long-term Debt, Current Maturities Term loan Short-term Debt Total current liabilities Liabilities, Current Long-term debt, net Long-term Debt, Excluding Current Maturities Deferred income taxes Deferred Tax Liabilities, Net, Noncurrent Pension and other liabilities Liability, Defined Benefit Plan, Noncurrent And Other Liabilities, Noncurrent Liability, Defined Benefit Plan, Noncurrent And Other Liabilities, Noncurrent Total liabilities Liabilities Total Westlake Chemical Corporation stockholders' equity Stockholders' Equity Attributable to Parent Noncontrolling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Total liabilities and equity Liabilities and Equity Employee Benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Total Available-for-sale Securities Available-for-sale Securities Proceeds from sales and maturities of securities Proceeds from Sale and Maturity of Available-for-sale Securities Gross realized gains Available-for-sale Securities, Gross Realized Gains Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Number of segments Number Of Segments Number of segments Number of major customers Concentration Risk, Number of Major Customers Concentration Risk, Number of Major Customers Number of Building Product Facilities Number Of Plants Represents the number of company plants that manufacture building products. Schedule Of Long-Term Debt Schedule of Long-term Debt Instruments [Table Text Block] Schedule of Cash Flow Information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Participating Securities, Distributed and Undistributed Earnings (Loss), Diluted Participating Securities, Distributed and Undistributed Earnings (Loss), Diluted Net income attributable to common shareholders Net Income Loss Available To Common Stockholders Net income available to common stockholders after adjustments for net income attributable to participating securities. Income Taxes Income Tax Disclosure [Text Block] Description of Business Description Of Business [Policy Text Block] Description Of Business [Policy Text Block] Acquisition of Axiall Corporation Acquisition of Axiall Corporation [Policy Text Block] Acquisition of Axiall Corporation [Policy Text Block] Westlake Chemical Partners LP Interest in Unincorporated Joint Ventures or Partnerships, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Concentration of Credit Risk Concentration Of Credit Risk [Policy Text Block] Disclosure of accounting policy for the concentration of credit risk. Allowance for Doubtful Accounts Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Inventories Inventory, Policy [Policy Text Block] Property, Plant and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Impairment of Long-Lived Assets and Impairment of Goodwill and Intangible Assets Impairment or Disposal of Long-Lived Assets, Including Intangible Assets, Policy [Policy Text Block] Property, Plant and Equipment, Planned Major Maintenance Activities, Policy [Policy Text Block] Property, Plant and Equipment, Planned Major Maintenance Activities, Policy [Policy Text Block] Business Combinations Business Combinations Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Foreign Currency Translation Foreign Currency Transactions and Translations Policy [Policy Text Block] Revenue Recognition Revenue Recognition Accounting Policy, Gross and Net Revenue Disclosure [Policy Text Block] Transportation and Freight Shipping and Handling Cost, Policy [Policy Text Block] Price Risk Management Derivatives, Policy [Policy Text Block] Asset Retirement Obligations Asset Retirement Obligation [Policy Text Block] Environmental Costs Environmental Costs, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Gross profit Income from operations Net income attributable to Westlake Chemical Corporation Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Balance at beginning of year Goodwill acquired during the year Goodwill, Acquired During Period Effects of changes in foreign exchange rates Goodwill, Foreign Currency Translation Gain (Loss) Goodwill, Purchase Accounting Adjustments Goodwill, Purchase Accounting Adjustments Balance at end of year Schedule of Business Acquisitions Schedule of Business Acquisitions, by Acquisition [Table Text Block] Schedule of Recognized Identified Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Pro Forma Information Business Acquisition, Pro Forma Information [Table Text Block] Current Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Foreign Current Foreign Tax Expense (Benefit) Total Current Current Income Tax Expense (Benefit) Deferred Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Foreign Deferred Foreign Income Tax Expense (Benefit) Total Deferred Other comprehensive (loss) income, net of income taxes Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Pension and other post-retirement benefits liability Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Pension and other post-retirement reserves adjustment (excluding amortization) Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax Amortization of benefits liability Income tax provision on pension and other post-retirement benefits liability Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Attributable to Parent Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax Income tax provision on foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax Available-for-sale investments Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax [Abstract] Unrealized holding gains (losses) on investments Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Reclassification Adjustments and Tax Reclassification of net realized gains to net income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Income tax benefit (provision) on available-for-sale investments Other Comprehensive Income (Loss) Income Tax (Provision) Benefit On Available For Sale Investment Amount of tax expense (benefit), including reclassification adjustments, of appreciation (loss) in value of available-for-sale securities. Excluded amounts related to other than temporary impairment (OTTI) loss. Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive income attributable to noncontrolling interests, net of tax of $1, $0 and $0 for 2017, 2016 and 2015, respectively Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Related Party And Affiliate Transactions Related Party Transactions Disclosure [Text Block] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Schedule of Multiemployer Plans [Table] Schedule of Multiemployer Plans [Table] Multiemployer Plans [Line Items] Multiemployer Plans [Line Items] Number of multiemployer plans Number Of Multiemployer Plans Number Of Multiemployer Plans Contributions to multi-employer plans Multiemployer Plans, Plan Contributions Debt Instrument, Interest Rate, Effective Percentage Debt Instrument, Interest Rate, Effective Percentage Weighted average interest rate on all long-term debt Long-term Debt, Weighted Average Interest Rate, at Point in Time Unamortized Debt Issuance Cost Unamortized Debt Issuance Expense Long-term Debt, Maturities, Repayments of Principal in Year Five Long-term Debt, Maturities, Repayments of Principal in Year Five Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Two Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Three Long-term Debt, Maturities, Repayments of Principal in Year Four Long-term Debt, Maturities, Repayments of Principal in Year Four Organization, Consolidation, And Presentation Of Financial Statements [Table] Organization, Consolidation, And Presentation Of Financial Statements [Table] Organization, Consolidation, And Presentation Of Financial Statements [Table] Westlake Chemical OpCo LP [Member] Westlake Chemical OpCo LP [Member] Westlake Chemical OpCo LP [Member] Subsidiaries [Member] Subsidiaries [Member] Partner Type [Axis] Partner Type [Axis] Partner Type of Partners' Capital Account, Name [Domain] Partner Type of Partners' Capital Account, Name [Domain] Limited Partner [Member] Limited Partner [Member] Louisiana LOUISIANA Kentucky KENTUCKY Subsidiary, Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock, Name of Transaction [Domain] Sale of Stock [Domain] IPO [Member] IPO [Member] Subsidiary of Common Parent [Member] Subsidiary of Common Parent [Member] Organization Consolidation And Presentation Of Financial Statements [Line Items] Organization consolidation and presentation of financial statements [Line Items]. Provisional adjustment of income tax benefit Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense (Benefit) Aggregate principal amount of senior notes Proceeds from Issuance of Senior Long-term Debt Maximum borrowing capacity Number of production facilities Number Of Production Facilities Number Of Production Facilities Limited partner interest (percent) Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest Capitalized interest Interest Costs Capitalized Asset Retirement Obligation, Current Asset Retirement Obligation, Current Asset Retirement Obligations, Noncurrent Asset Retirement Obligations, Noncurrent Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Deferred Income Tax [Member] Deferred Income Tax Charge [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer relationships [Member] Customer Relationships [Member] Trade Name [Member] Trade Names [Member] Technology [Member] Technology-Based Intangible Assets [Member] Supply Contracts and Leases [Member] Supply Contracts and Leases [Member] Supply Contracts and Leases [Member] Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Cash Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Accounts Receivable Business Combination, Acquired Receivable, Fair Value Income tax receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets, Current Inventories Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory Prepaid expenses and other current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Property, plant and equipment Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Finite-lived intangibles Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles Other assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets Total assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Accounts and notes payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable Interest payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Interest Payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Interest Payable Income tax payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities, Current Accrued compensation Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Compensation Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Compensation Accrued liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accrued Liabilities Deferred income taxes Business 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Liabilities Total identifiable net assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Noncontrolling interest Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value Total fair value allocated to net assets acquired Business Combination, Acquired Receivables, Gross Contractual Amount Business Combination, Acquired Receivables, Gross Contractual Amount Business Combination, Acquired Receivables, Estimated Uncollectible Business Combination, Acquired Receivables, Estimated Uncollectible Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments Related to Previous Period Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments Related to Previous Period Inventories Inventory Disclosure [Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Exchange Offer Percentage Exchange Offer Percentage Exchange Offer Percentage Debt Instrument, Redemption Price, Percentage Debt Instrument, Redemption Price, Percentage 6 1/2% GO Zone Tax-Exempt Revenue Bonds Due 2035 [Member] Go Zone 3.50% Bonds Due 2032 [Member] Go Zone Three Point Five Percent Bonds Due Twenty Thirty Two [Member] Go Zone Three Point Five Percent Bonds Due Twenty Thirty Two [Member] Debt Instrument, Face Amount Debt Instrument, Face Amount Extinguishment of Debt, Amount Extinguishment of Debt, Amount Amount of bonds remarketed Debt Instrument, Bonds, Principal Amount Remarketed Debt Instrument, Bonds, Principal Amount Remarketed Fixed Charge Coverage Ratio Fixed Charge Coverage Ratio The calculated fixed charge coverage ratio. Maximum Unrestricted Quarterly Dividends Allowable Under Debt Covenants Maximum Unrestricted Quarterly Dividends Allowable Under Debt Covenants The maximum unrestricted payment per share allowed under debt covenants for the quarterly dividend. Maximum Unrestricted Distributions Allowable Under Debt Covenants Maximum Unrestricted Distributions Allowable Under Debt Covenants The maximum unrestricted distribution allowed under debt covenants. Distributions in excess of this amount are subject to certain restrictions. Maximum Percentage Of Income Distribution Maximum Percentage Of Income Distribution Maximum percentage of income distribution, subject to certain other distribution terms. Maximum Distribution Percentage Of Specified Net Cash Proceeds Maximum Distribution Percentage Of Specified Net Cash Proceeds Maximum distribution percentage of specified net cash proceeds received after a stated period plus other adjustments, and subject to certain other distribution terms. Depreciation expense on property, plant and equipment Depreciation 2018 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Five Number of defined benefit plans amended Number of Defined Benefit Plans Amended Number of Defined Benefit Plans Amended Expected future contributions in the next fiscal year Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year Net operating loss carryforward Deferred Tax Assets, Operating Loss Carryforwards Credit carryforward Deferred Tax Assets, Tax Credit Carryforwards Accruals Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities Pension Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Pensions Allowance for doubtful accounts Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Inventories Deferred Tax Assets, Inventory Other Deferred Tax Assets, Other Deferred taxes assets—total Deferred Tax Assets, Gross Property, plant and equipment Deferred Tax Liabilities, Property, Plant and Equipment Intangibles Deferred Tax Liabilities, Other Finite-Lived Assets Turnaround costs Deferred Tax Liabilities, Deferred Expense, Other Capitalized Costs Basis difference—consolidated partnerships Deferred Tax Liabilities, Parent's Basis In Consolidated Partnerships Deferred Tax Liabilities, Parent's Basis In Consolidated Partnerships Other Deferred Tax Liabilities, Other Deferred tax liabilities—total Deferred Tax Liabilities, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Total net deferred tax liabilities Deferred Tax Liabilities, Net Balance sheet classifications Deferred Tax Assets, Net, Classification [Abstract] Noncurrent deferred tax asset Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Noncurrent deferred tax liability Net income (loss) Net changes in working capital and other Increase (Decrease) in Operating Capital Intercompany financing Proceeds From Repayments Of Intercompany Financing Proceeds from (Repayments of) Intercompany Financing Receivable under the investment management agreement Receivable under Investment Management Agreement Financing Activity Receivable under Investment Management Agreement Financing Activity Debt issuance costs Net proceeds from issuance of Westlake Partners common units Repayment of term loan Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Amortization of pension and other post-retirement items Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Benefit from income taxes Reclassification from AOCI, Current Period, Tax Provision for (benefit from) income taxes, investments Income (Loss) from Continuing Operations, including portion attributable to noncontrolling interest Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Total reclassifications for the period Schedule Of Accounts Receivable Schedule Of Accounts And Financing Receivables [Text Block] Tabular disclosure of the various categories of receivables, including trade and other receivables, and for each the gross carrying value, allowance (if appropriate), and net carrying value as of the balance sheet date. Net sales Business Acquisition, Pro Forma Revenue Net income Business Acquisition, Pro Forma Net Income (Loss) Net income (loss) attributable to noncontrolling interest BusinessAcquisitionProFormaNetIncomeLossAttributabletoNoncontrollingInterest Business Acquisition Pro Forma Net Income Loss Attributable to Noncontrolling Interest Net income attributable to Westlake Chemical Corporation Business Acquisition, Pro Forma net Income (Loss) Attributable to Parent Business Acquisition, Pro Forma net Income (Loss) Attributable to Parent Basic (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Diluted (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Divestitures Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Restructuring Costs Restructuring Costs Legal and Settlement Claims, net Loss Contingency, Loss in Period Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Business Combination Bargain Purchase Gain Net Of Related Expenses Business Combination Bargain Purchase Gain Net Of Related Expenses Bargain purchase gain, net of related expenses. Accrued Liabilities Accrued Liabilities [Abstract] Accrued rebates Accrued Rebates, Current Accrued Rebates, Current Accrued Income Taxes, Current Accrued Income Taxes, Current Non-Cash Investing Activity [Abstract] Non-Cash Investing Activity [Abstract] Non-Cash Investing Activity [Abstract] Increase (Decrease) in Capital Expenditure Accrual Increase (Decrease) in Capital Expenditure Accrual Increase (Decrease) in Capital Expenditure Accrual Remeasurement gain (loss) Cash Flow Information Supplemental Cash Flow Information [Abstract] Interest paid, net of interest capitalized Interest Paid, Net Income taxes paid Income Taxes Paid, Net Licenses and intellectual property [Member] Licensing Agreements [Member] Trademarks [Member] Trademarks [Member] Other [Member] Other Intangible Assets [Member] Total Other Intangible Assets [Member] Total Other Intangible Assets [Member] Total Other Intangible Assets [Member] Goodwill and Intangible Assets Disclosure [Abstract] Finite-Lived Customer Relationships, Gross Finite-Lived Customer Relationships, Gross Finite-Lived License Agreements, Gross Finite-Lived License Agreements, Gross Finite-Lived Trademarks, Gross Finite-Lived Trademarks, Gross Other Intangible Assets, Gross Other Finite-Lived Intangible Assets, Gross Intangible assets, Cost Finite-Lived Intangible Assets, Gross Intangible assets, Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Weighted Average Life Finite-Lived Intangible Asset, Useful Life Westlake Chemical Partners LP [Member] Westlake Chemical Partners LP [Member] Westlake Chemical Partners LP [Member] Partners' Capital Account, Units, Sold in Public Offering Partners' Capital Account, Units, Sold in Public Offering Sale of Unit Price Per Unit Sale of Unit Price Per Unit Per unit amount received by subsidiary or equity investee for each unit issued or sold in the unit transaction. Net proceeds from WLKP LP common stock units Payments of Stock Issuance Costs Payments of Stock Issuance Costs Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest Limited Partnership Ownership Percentage Increase Limited Partnership Ownership Percentage Increase Limited Partnership Ownership Percentage Increase Net loss (gain) Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Total before tax Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Accumulated other comprehensive income (loss), benefits, net of tax Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Components of Income (Loss) Before Income Taxes Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule of The Provision For (Benefit From) Income Taxes Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Reconciliation of Taxes Computed at the Statutory Rate to Income Tax Expense Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Deferred Tax Assets And Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Realized Gain (Loss) Schedule of Realized Gain (Loss) [Table Text Block] Foreign and state net operating loss carryforwards Operating Loss Carryforwards Change in valuation allowance Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Provisional tax expense related to one-time repatriation Tax Cuts and Jobs Act of 2017,Incomplete Accounting, Transition Taxfor Accumulated Foreign Earnings,Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017,Incomplete Accounting, Transition Taxfor Accumulated Foreign Earnings,Provisional Income Tax Expense (Benefit) Foreign tax Tax Cuts and Jobs Act of 2017, Foreign Tax on Accumulated Earnings of Foreign Subsidiary No Longer Permanently Reinvested Tax Cuts and Jobs Act of 2017, Foreign Tax on Accumulated Earnings of Foreign Subsidiary No Longer Permanently Reinvested Statement of Stockholders' Equity [Abstract] Common Stock, Held In Treasury [Member] Treasury Stock [Member] Additional Paid-In Capital [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Noncontrolling Interests [Member] Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Number of shares, beginning balance Shares, Issued Other comprehensive income (loss) Common stock repurchased, shares Treasury Stock, Shares, Acquired Common stock repurchased Treasury Stock, Value, Acquired, Cost Method Shares issued—stock- based compensation, shares Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Shares issued—stock- based compensation Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Stock-based compensation, net of tax on stock options exercised (in shares) Stock-based compensation, net of tax on stock options exercised Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Dividends declared Dividends, Common Stock, Cash Distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Issuance of Westlake Chemical Partners LP common units Noncontrolling Interest, Increase from Subsidiary Equity Issuance Number of shares, ending balance Schedule of Estimated Useful Lives of Assets Schedule Of Estimated Useful Lives Of Assets [Table Text Block] Table of estimated useful lives of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Supplemental Information Additional Financial Information Disclosure [Text Block] Number Of Subsidiaries Company Provides Post Retirement Healthcare Benefit Number Of Subsidiaries Company Provides Post Retirement Healthcare Benefit Number of subsidiaries, whose employees meet certain minimum age and service requirements, that are provided post-retirement healthcare benefits by the Company. Change in benefit obligation Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Benefit obligation, beginning of year Defined Benefit Plan, Benefit Obligation Benefit obligation assumed with acquisition Defined Benefit Plan, Benefit Obligation, Business Combination Service cost Defined Benefit Plan, Service Cost Interest Cost Defined Benefit Plan, Benefit Obligation, Interest Cost Defined Benefit Plan, Benefit Obligation, Interest Cost Actuarial loss (gain) Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Settlements Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement Foreign exchange effects Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss) Benefit obligation, end of year Change in plan assets Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Fair value of plan assets, beginning of year Acquisition Defined Benefit Plan, Plan Assets, Business Combination Actual return Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Employer contribution Defined Benefit Plan, Plan Assets, Contributions by Employer Plan participants' contributions Defined Benefit Plan, Plan Assets, Contributions by Plan Participant Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid Administrative expenses paid Defined Benefit Plan, Plan Assets, Administration Expense Settlements Defined Benefit Plan, Plan Assets, Payment for Settlement Foreign exchange effects Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss) Fair value of plan assets, end of year Funded status, end of year Defined Benefit Plan, Funded (Unfunded) Status of Plan Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Health care cost trend rate - Initial rate Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Health care cost trend rate- Ultimate rate (periodic benefit costs) Defined Benefit Plan, Ultimate Health Care Cost Trend Rate Health care cost trend rate- Ultimate rate (benefit obligation) Defined Benefit Plan, Defined Benefit Obligation, Ultimate Health Care Cost Trend Rate Defined Benefit Plan, Defined Benefit Obligation, Ultimate Health Care Cost Trend Rate Health care cost trend rate- Years to ultimate (benefit obligations) Defined Benefit Plan, Years To Health Care Cost Trend Rate Reaches Ultimate Trend Rate, Benefit Obligation Defined Benefit Plan, Years To Health Care Cost Trend Rate Reaches Ultimate Trend Rate, Benefit Obligation Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase Discount rate for benefit obligations Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Discount rate for service cost Defined Benefit Plan, Assumptions Used Calculating Service Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Service Cost, Discount Rate Discount rate for interest cost Defined Benefit Plan, Assumptions Used Calculating Interest Cost, Discount Rate Defined Benefit Plan, Assumptions Used Calculating Interest Cost, Discount Rate Expected return on plan assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets Rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Health care cost trend rate- Initial rate (periodic benefit costs) Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year, Periodic Benefit Costs Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year, Periodic Benefit Costs Health care cost trend rate- Years to ultimate (periodic benefit costs) Defined Benefit Plan, Years To Health Care Cost Trend Rate Reaches Ultimate Trend Rate Defined Benefit Plan, Years To Health Care Cost Trend Rate Reaches Ultimate Trend Rate Unamortized Premium (Discount) and Debt Issuance Costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Long-term debt, net Long-term Debt Long-Term Debt, Gross, Current Maturities Long-Term Debt, Gross, Current Maturities Amount, before unamortized (discount) premium and debt issuance cost, of long-term debt, classified as current. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. Debt Instrument, Unamortized Premium (Discount) and debt issuance cost, net, Current Maturities Debt Instrument, Unamortized Discount (Premium) and debt issuance cost, net, Current Maturities Amount of unamortized debt discount (premium) and debt issuance costs, of long-term debt, classified as current. Long-term Debt, Current Maturities Long-term Debt, Gross Excluding Current Maturities Long-term Debt, Gross Excluding Current Maturities Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt debt classifed as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but is not limited to, notes payable, bonds payable, commercial loans, convertible debt, subordinated debt and other types of debt. Excludes capital lease obligations. Debt Instrument, Unamortized Premium (Discount) and Debt Issuance Cost, Net, Excluding Current Maturities Debt Instrument, Unamortized Discount (premium) and Debt Issuance Cost, Net, Excluding Current Maturities Debt Instrument, Unamortized Discount (premium) and Debt Issuance Cost, Net, Excluding Current Maturities. Long-term Debt, Excluding Current Maturities Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Term Loan Facility Maturing March 31, 2017 [Member] Term Loan Facility Maturing March 31, 2017 [Member] Term Loan Facility Maturing March 31, 2017 [Member] Note Payable to Bank Borrowing Notes Payable to Bank Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Total Assets Reconciliation of Assets from Segment to Consolidated [Table Text Block] Reconciliation Of Total Segment Income From Operations To Consolidated Income Before Income Taxes Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] Geographic Information For Sales To External Customers And Long-Lived Assets Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Operating Leases, Rent Expense Operating Leases, Rent Expense, Net Operating Leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2018 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2019 Operating Leases, Future Minimum Payments, Due in Two Years 2020 Operating Leases, Future Minimum Payments, Due in Three Years 2021 Operating Leases, Future Minimum Payments, Due in Four Years 2022 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total minimum lease payments Operating Leases, Future Minimum Payments Due Capital Leases Capital Leases, Future Minimum Payments, Net Minimum Payments, Fiscal Year Maturity [Abstract] 2018 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2019 Capital Leases, Future Minimum Payments Due in Two Years 2020 Capital Leases, Future Minimum Payments Due in Three Years 2021 Capital Leases, Future Minimum Payments Due in Four Years 2022 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total minimum lease payments Capital Leases, Future Minimum Payments Due Less: Imputed interest costs Capital Leases, Future Minimum Payments, Interest Included in Payments Present value of net minimum lease payments Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Commitments And Contingencies Commitments and Contingencies Disclosure [Text Block] Accumulated Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Finite-Lived Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Weighted-average vesting period (in years) Weighted average fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected life in years Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Schedule Of Inventory Schedule of Inventory, Current [Table Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Dividends [Axis] Dividends [Axis] Dividends [Domain] Dividends [Domain] Ordinary Dividend [Member] Ordinary Dividend [Member] Ordinary Dividend [Member] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] 2011 Program [Member] 2011 Program [Member] 2011 Program [Member] 2014 Program [Member] 2014 Program [Member] 2014 Program [Member] Class of Stock [Line Items] Class of Stock [Line Items] Dividends, Common Stock, Cash Common Stock, Voting Rights, Number of Votes Per Share Common Stock, Voting Rights, Number of Votes Per Share Common Stock, Voting Rights, Number of Votes Per Share Common stock, sinking fund Common Stock Sinking Fund Provision Sinking fund provision for common stock. Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Stock repurchased 2011 program, shares repurchased Stock Repurchase Program, Shares Repurchased, Gross Stock Repurchase Program, Shares Repurchased, Gross Aggregate purchase price of common stock repurchased Treasury Stock, Value, Cost Method Equity impact of the cost of common stock that were repurchased by the entity. Recorded using the cost method. Stock repurchased 2014 program, shares repurchase Condensed Consolidating Financial Information Balance Sheet Condensed Balance Sheet [Table Text Block] Condensed Consolidating Financial Information Statement Of Operations Condensed Income Statement [Table Text Block] Condensed Consolidating Financial Information Statement Of Cash Flows Condensed Cash Flow Statement [Table Text Block] 5.0% Senior Notes Due 2046 [Member] Five Point Zero Percentage Senior Notes Due Twenty Forty Six [Member] Five Point Zero Percentage Notes Due Twenty Forty Six [Member] Property, Plant And Equipment Property, Plant and Equipment Disclosure [Text Block] 3.60%, 5.0%, 4.625%, 4.875% Senior Notes [Member] 3.60%, 5.0%, 4.625%, 4.875% Senior Notes [Member] 3.60%, 5.0%, 4.625%, 4.875% Senior Notes [Member] Senior notes, minimum debt amount guaranteed by subsidiaries Debt Amount In Excess Of Guaranteed By Subsidiaries Debt amount in excess of guaranteed by subsidiaries. Intersegment Eliminations [Member] Intersegment Eliminations [Member] Polyethylene [Member] Polyethylene [Member] Polyethylene [Member] Styrene, Feedstock And Other [Member] Styrene, Feedstock And Other [Member] Styrene, Feedstock And Other [Member] PVC, Caustic Soda And Other [Member] Pvc Caustic Soda And Other [Member] PVC, caustic soda and other [Member] Building Products [Member] Building Products [Member] Building Products [Member] Provision for (benefit from) income taxes Payments to Acquire Property, Plant, and Equipment Unconditional purchase obligations Purchase Obligation, Fiscal Year Maturity [Abstract] 2018 Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months 2019 Unrecorded Unconditional Purchase Obligation, Due within Two Years 2020 Unrecorded Unconditional Purchase Obligation, Due within Three Years 2021 Unrecorded Unconditional Purchase Obligation, Due within Four Years 2022 Unrecorded Unconditional Purchase Obligation, Due within Five Years Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Axis] Exercise Price Range [Axis] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] $7.12 - $9.65 [Member] Range One [Member] Range one [Member] $10.26 - $18.05 [Member] Range Two [Member] Range two [Member] $22.92 - $30.05 [Member] Range Three [Member] Range three [Member] $40.38 - $52.35 [Member] Range Four [Member] Range four [Member] $61.87 - $68.18 [Member] Range Five [Member] Range Five [Member] Range of exercise prices, minimum (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Range of exercise prices, maximum (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Options Outstanding Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options Weighted Average Remaining Contractual Life (Years) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term Other income (expense), net Equity in net income of subsidiaries Income Loss From Equity Method Investments Subsidiaries Income loss from equity method investments and subsidiaries. Comprehensive income attributable to Westlake Chemical Corporation ASSETS Assets [Abstract] Current assets Assets, Current [Abstract] Restricted cash Restricted Cash and Investments, Current LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Current liabilities Liabilities, Current [Abstract] Pension and other post-retirement benefits Other liabilities Other Liabilities, Noncurrent Stockholders' equity Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued and outstanding Preferred Stock, Value, Issued Common stock, $0.01 par value, 300,000,000 shares authorized; 134,651,380 and 134,651,380 shares issued at December 31, 2017 and 2016, respectively Common Stock, Value, Issued Common stock, held in treasury, at cost; 5,232,875 and 5,726,377 shares at December 31, 2017 and 2016, respectively Treasury Stock, Value Additional paid-in capital Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total Westlake Chemical Corporation stockholders' equity Land Land Buildings and improvements Buildings and Improvements, Gross Plant and equipment Machinery and Equipment, Gross Other Property, Plant and Equipment, Other, Gross Property, Plant and Equipment, Gross Property, Plant and Equipment, Gross Less: Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property, plant and equipment, net, before construction in progress Property, Plant and Equipment, Net Excluding Construction In-Progress Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. Does not include construction in progress. Construction in progress Construction in Progress, Gross Property, plant and equipment, net