Westlake (WLK) 10-Q 6 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 29, 2015
Document Documentand Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	WLK
Entity Registrant Name	WESTLAKE CHEMICAL CORP
Entity Central Index Key	1262823
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		132,861,942

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets
Cash and cash equivalents	$945,649	$880,601
Accounts receivable, net	527,127	560,666
Inventories	480,380	525,776
Prepaid expenses and other current assets	18,018	11,807
Deferred income taxes	30,988	32,437
Total current assets	2,002,162	2,011,287
Property, plant and equipment, net	2,751,486	2,757,557
Equity investments	64,721	61,305
Other assets, net
Intangible assets, net	207,254	218,431
Deferred charges and other assets	154,162	165,410
Total other assets, net	361,416	383,841
Total assets	5,179,785	5,213,990
Current liabilities
Accounts payable	247,493	261,062
Accrued liabilities	205,714	276,118
Total current liabilities	453,207	537,180
Long-term debt	764,027	763,997
Deferred income taxes	534,679	536,066
Other liabilities	157,130	174,859
Total liabilities	1,909,043	2,012,102
Commitments and contingencies (Notes 7 and 16)
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; 134,679,064 and 134,679,064 shares issued at March 31, 2015 and December 31, 2014, respectively	1,347	1,347
Common stock, held in treasury, at cost; 1,817,122 and 1,787,546 shares at March 31, 2015 and December 31, 2014, respectively	-98,275	-96,372
Additional paid-in capital	534,542	530,441
Retained earnings	2,679,906	2,555,528
Accumulated other comprehensive loss	-137,662	-79,433
Total Westlake Chemical Corporation stockholders' equity	2,979,858	2,911,511
Noncontrolling interests	290,884	290,377
Total equity	3,270,742	3,201,888
Total liabilities and equity	$5,179,785	$5,213,990

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value	$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	$0.01	$0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	134,679,064	134,679,064
Common stock, held in treasury	1,817,122	1,787,546

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Net sales	$1,103,531	$1,027,676
Cost of sales	818,985	740,666
Gross profit	284,546	287,010
Selling, general and administrative expenses	55,266	38,955
Income from operations	229,280	248,055
Other income (expense)
Interest expense	-9,591	-9,157
Other income, net	9,096	2,509
Income before income taxes	228,785	241,407
Provision for income taxes	78,378	83,375
Net income	150,407	158,032
Net income attributable to noncontrolling interests	4,065	0
Net income attributable to Westlake Chemical Corporation	$146,342	$158,032
Earnings per common share attributable to Westlake Chemical Corporation
Basic	$1.10	$1.18
Diluted	$1.10	$1.18
Weighted average shares outstanding:
Basic	132,714,566	133,072,254
Diluted	133,205,306	133,612,924
Dividends per common share	$0.17	$0.13

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$150,407	$158,032
Pension and other post-retirement benefits liability
Amortization of benefits liability	652	219
Income tax provision on pension and other post-retirement benefits liability	-225	-84
Foreign currency translation adjustments	-59,698	-898
Available-for-sale investments
Unrealized holding gains on investments	1,626	2,467
Reclassification of net realized loss to net income	0	25
Income tax provision on available-for-sale investments	-584	-895
Other comprehensive (loss) income	-58,229	834
Comprehensive income	92,178	158,866
Comprehensive income attributable to noncontrolling interests, net of tax	4,065	0
Comprehensive income (loss) attributable to Westlake Chemical Corporation	$88,113	$158,866

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities
Net income	$150,407	$158,032
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	58,641	45,972
Recovery of doubtful accounts	-9	-144
Amortization of debt issuance costs	501	365
Stock-based compensation expense	2,340	2,222
Loss from disposition of fixed assets	133	855
Deferred income taxes	5,331	8,275
Windfall tax benefits from share-based payment arrangements	-1,701	-3,512
Income from equity method investments, net of dividends	-3,416	-685
Other (losses) gains, net	-554	444
Changes in operating assets and liabilities
Accounts receivable	18,517	5,332
Inventories	35,979	32,870
Prepaid expenses and other current assets	-6,202	-1,478
Accounts payable	-3,625	-29,706
Accrued liabilities	-59,585	-4,952
Other, net	-6,201	-1,385
Net cash provided by operating activities	190,556	212,505
Cash flows from investing activities
Additions to property, plant and equipment	-95,822	-110,741
Proceeds from disposition of assets	0	12
Proceeds from sales and maturities of securities	0	30,119
Purchase of securities	0	-49,025
Settlements of derivative instruments	-833	-409
Net cash used for investing activities	-96,655	-130,044
Cash flows from financing activities
Dividends paid	-21,964	-16,789
Distributions to noncontrolling interests	-3,558	0
Proceeds from exercise of stock options	157	2,158
Repurchase of common stock for treasury	-2,000
Windfall tax benefits from share-based payment arrangements	1,701	3,512
Net cash provided by financing activities	-25,664	-11,119
Effect of exchange rate changes on cash and cash equivalents	-3,189	0
Net increase in cash and cash equivalents	65,048	71,342
Cash and cash equivalents at beginning of period	880,601	461,301
Cash and cash equivalents at end of period	$945,649	$532,643

Basis_of_Financial_Statements

Basis of Financial Statements	3 Months Ended
	Mar. 31, 2015
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, 2014 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, 2014 (the "2014 Form 10-K"), filed with the SEC on February 25, 2015. These 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, 2014.
	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 March 31, 2015, its results of operations for the three months ended March 31, 2015 and 2014 and the changes in its cash position for the three months ended March 31, 2015 and 2014.
	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, 2015 or any other interim period. The preparation of 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.
	Recent Accounting Pronouncements
	Revenue from Contracts with Customers
	In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede the existing 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 will be 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 either "full retrospective" adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or "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 accounting standard will be effective for reporting periods beginning after December 15, 2016. The Company is in the process of evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations and cash flows.
	Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items
	In January 2015, the FASB issued an accounting standards update to simplify income statement classification by removing the concept of extraordinary items from U.S. GAAP. Under the new standard, an unusual and infrequent event or transaction is no longer allowed to be separately disclosed as "extraordinary." The standard retains the existing requirement to separately present items that are of an unusual nature or occur infrequently on a pre-tax basis within income from continuing operations. The new guidance also requires similar separate presentation of items that are both unusual and infrequent on a pre-tax basis within income from continuing operations. The standard allows for either prospective or retrospective application. If adopted prospectively, both the nature and amount of any subsequent adjustments to previously reported extraordinary items must be disclosed. The accounting standard will be effective for reporting periods beginning after December 15, 2015 and is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows.
	Amendments to the Consolidation Analysis
	In February 2015, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect both the variable interest entity and voting interest entity consolidation models. The new standard changes the consideration of substantive rights, related party interests and fees paid to the decision maker when applying the variable interest entity consolidation model and eliminates certain guidance for limited partnerships and similar entities under the voting interest consolidation model. The accounting standard will be effective for annual periods beginning after December 15, 2015. The Company is in the process of evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations and cash flows.
	Simplifying the Presentation of Debt Issuance Costs
	In April 2015, the FASB issued an accounting standards update on simplifying the presentation of debt issuance costs, which requires all costs incurred to issue debt to be presented in the balance sheet as a direct deduction from the carrying value of the associated debt liability, consistent with the presentation of a debt discount. The accounting standard will be effective for reporting periods beginning after December 15, 2015, and interim periods within those fiscal years, and is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows.

Financial_Instruments

Financial Instruments	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments
	Cash Equivalents
	The Company had $496,843 and $509,811 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at March 31, 2015 and December 31, 2014, respectively. The Company's investments in held-to-maturity securities are held at amortized cost, which approximates fair value.
	Available-for-Sale Marketable Securities
	Investments in available-for-sale securities were classified as follows:
		March 31,			December 31,
		2015			2014
	Non-current	$	17,033		$	15,414
	Total available-for-sale securities	$	17,033		$	15,414
	The cost, gross unrealized gains, gross unrealized losses and fair value of the Company's available-for-sale securities were as follows:
			March 31, 2015
			Cost			Gross			Gross		Fair Value
						Unrealized			Unrealized
						Gains			Losses
	Equity securities		$	15,043		$	1,990		$	—	$	17,033
	Total available-for-sale securities		$	15,043		$	1,990		$	—	$	17,033
			December 31, 2014
			Cost			Gross			Gross		Fair Value
						Unrealized			Unrealized
						Gains			Losses
	Equity securities		$	15,050		$	364		$	—	$	15,414
	Total available-for-sale securities		$	15,050		$	364		$	—	$	15,414
	As of March 31, 2015 and December 31, 2014, net unrealized gains on the Company's available-for-sale securities of $1,276 and $233, respectively, net of income tax expense of $714 and $131, respectively, were recorded in accumulated other comprehensive income. See Note 12 for the fair value hierarchy of the Company's available-for-sale securities.
	The proceeds from sales and maturities of available-for-sale securities and the gross realized gains and losses included in the consolidated statements of operations are reflected in the table below. The cost of securities sold was determined using the specific identification method. There were no sales or maturities of available-for-sale securities during the three months ended March 31, 2015.
			Three Months Ended March 31,
			2015			2014
	Proceeds from sales and maturities of securities		$	—		$	30,119
	Gross realized gains		—			13
	Gross realized losses		—			(38		)

Accounts_Receivable

Accounts Receivable	3 Months Ended
	Mar. 31, 2015
Accounts Receivable, Net [Abstract]
Accounts Receivable	Accounts Receivable
	Accounts receivable consist of the following:
		March 31,			December 31,
		2015			2014
	Trade customers	$	500,262		$	525,546
	Affiliates	449			437
	Allowance for doubtful accounts	(13,259		)	(13,468		)
		487,452			512,515
	Federal and state taxes	21,289			8,919
	Other	18,386			39,232
	Accounts receivable, net	$	527,127		$	560,666

Inventories

Inventories	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Inventories	Inventories
	Inventories consist of the following:
		March 31,		December 31,
		2015		2014
	Finished products	$	278,501	$	300,909
	Feedstock, additives and chemicals	135,903		158,635
	Materials and supplies	65,976		66,232
	Inventories	$	480,380	$	525,776

Property_Plant_and_Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment
	As of March 31, 2015, the Company had property, plant and equipment, net totaling $2,751,486. The Company assesses these assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, including when negative conditions such as significant current or projected operating losses exist. Other factors considered by the Company when determining if an impairment assessment is necessary include, but are not limited to, significant changes or projected changes in supply and demand fundamentals (which would have a negative impact on operating rates or margins), new technological developments, new competitors with significant raw material or other cost advantages, adverse changes associated with the U.S. and world economies and uncertainties associated with governmental actions. Long-lived assets assessed for impairment are grouped at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities.
	Depreciation expense on property, plant and equipment of $49,658 and $38,061 is included in cost of sales in the consolidated statements of operations for the three months ended March 31, 2015 and 2014, respectively.

Other_Assets

Other Assets	3 Months Ended
	Mar. 31, 2015
Other Assets [Abstract]
Other Assets	Other Assets
	Amortization expense on intangible and other assets of $9,484 and $8,276 is included in the consolidated statements of operations for the three months ended March 31, 2015 and 2014, respectively.
	Goodwill
	Goodwill for the Olefins segment was $29,990 at March 31, 2015 and December 31, 2014. Goodwill for the Vinyls segment was $32,026 at March 31, 2015 and December 31, 2014. There were no changes in the carrying amount of goodwill by operating segments for the three months ended March 31, 2015.

LongTerm_Debt

Long-Term Debt	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt
	Long-term debt consists of the following:
		March 31,		December 31,
		2015		2014
	3.60% senior notes due 2022	$	249,138	$	249,108
	6 ½% senior notes due 2029	100,000		100,000
	6 ¾% senior notes due 2032	250,000		250,000
	6 ½% senior notes due 2035 (the "6 ½% GO Zone Senior Notes Due 2035")	89,000		89,000
	6 ½% senior notes due 2035 (the "6 ½% IKE Zone Senior Notes Due 2035")	65,000		65,000
	Loan related to tax-exempt waste disposal revenue bonds due 2027	10,889		10,889
	Long-term debt, net	$	764,027	$	763,997
	Revolving Credit Facility
	The Company has a $400,000 senior secured revolving credit facility. The facility includes a provision permitting the Company to increase the size of the facility, up to four times, in increments of at least $25,000 each (up to a maximum of $200,000) under certain circumstances if the lenders agree to commit to such an increase. At March 31, 2015, the Company had no borrowings outstanding under the revolving credit facility. Any borrowings under the facility will bear interest at either LIBOR plus a spread ranging from 1.25% to 1.75%, provided that so long as the Company is rated investment grade, the margin for LIBOR loans will not exceed 1.50%, or a base rate plus a spread ranging from 0.00% to 0.50%. The revolving credit facility also requires an unused commitment fee of 0.25% per annum. All interest rates under the facility are subject to monthly grid pricing adjustments based on prior month average daily loan availability. The revolving credit facility matures on July 17, 2019. As of March 31, 2015, the Company had outstanding letters of credit totaling $29,959 and borrowing availability of $370,041 under the revolving credit facility.

Stockholders_Equity

Stockholders Equity	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity
	Changes in stockholders' equity for the three months ended March 31, 2015 and 2014 were as follows:
			Common				Common				Additional		Retained			Accumulated Other Comprehensive			Noncontrolling Interests			Total
			Stock				Stock,				Paid-in		Earnings			Income (Loss)
							Held in				Capital
							Treasury
	Balances at December 31, 2014		$	1,347			$	(96,372	)		$	530,441	$	2,555,528		$	(79,433	)	$	290,377		$	3,201,888
	Net income		—				—				—		146,342			—			4,065			150,407
	Other comprehensive income
	(loss), net of income taxes:
	Pension and other post-		—				—				—		—			427			—			427
	retirement benefits
	liability
	Foreign currency		—				—				—		—			(59,698		)	—			(59,698		)
	translation adjustments
	Net unrealized holding		—				—				—		—			1,042			—			1,042
	gains on investments
	Common stock repurchased		—				(2,000		)		—		—			—			—			(2,000		)
	Shares issued—stock-		—				97				60		—			—			—			157
	based compensation
	Stock-based compensation,		—				—				4,041		—			—			—			4,041
	net of tax on stock options
	exercised
	Dividends paid		—				—				—		(21,964		)	—			—			(21,964		)
	Distributions to noncontrolling		—				—				—		—			—			(3,558		)	(3,558		)
	interests
	Balances at March 31, 2015		$	1,347			$	(98,275	)		$	534,542	$	2,679,906		$	(137,662	)	$	290,884		$	3,270,742
			Common				Common				Additional		Retained			Accumulated Other Comprehensive			Total
			Stock				Stock,				Paid-in		Earnings			Income (Loss)
							Held in				Capital
							Treasury
	Balances at December 31, 2013		$	1,346			$	(46,220	)		$	511,432	$	1,954,661		$	(2,616	)	$	2,418,603
	Net income		—				—				—		158,032			—			158,032
	Other comprehensive income (loss), net of
	income taxes:
	Pension and other post-retirement benefits		—				—				—		—			135			135
	liability
	Foreign currency translation adjustments		—				—				—		—			(898		)	(898		)
	Net unrealized holding gains on		—				—				—		—			1,597			1,597
	investments
	Shares issued—stock-based compensation		1				—				2,157		—			—			2,158
	Stock-based compensation, net of tax on stock		—				—				5,734		—			—			5,734
	options exercised
	Dividends paid		—				—				—		(16,789		)	—			(16,789		)
	Balances at March 31, 2014		$	1,347			$	(46,220	)		$	519,323	$	2,095,904		$	(1,782	)	$	2,568,572
	Accumulated Other Comprehensive Loss
	Changes in accumulated other comprehensive income (loss) by component for the three months ended March 31, 2015 and 2014 were as follows:
			Benefits				Cumulative				Net Unrealized		Total
			Liability,				Foreign				Holding Gains
			Net of Tax				Currency				on Investments,
							Exchange				Net of Tax
	Balances at December 31, 2014		$	(23,442	)		$	(56,224	)		$	233	$	(79,433	)
	Other comprehensive (loss) income before		—				(59,698		)		1,042		(58,656		)
	reclassifications
	Amounts reclassified from accumulated other		427				—				—		427
	comprehensive loss
	Net other comprehensive income (loss) for the period		427				(59,698		)		1,042		(58,229		)
	Balances at March 31, 2015		$	(23,015	)		$	(115,922	)		$	1,275	$	(137,662	)
			Benefits				Cumulative				Net Unrealized		Total
			Liability,				Foreign				Holding Gains
			Net of Tax				Currency				on Investments,
							Exchange				Net of Tax
	Balances at December 31, 2013		$	(6,696	)		$	3,904			$	176	$	(2,616	)
	Other comprehensive (loss) income before		—				(898		)		1,581		683
reclassifications
Amounts reclassified from accumulated other		135				—				16		151
comprehensive loss
Net other comprehensive income (loss) for the period		135				(898		)		1,597		834
Balances at March 31, 2014		$	(6,561	)		$	3,006			$	1,773	$	(1,782	)
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 months ended March 31, 2015 and 2014:
Details about Accumulated Other Comprehensive		Location of Reclassification		Three Months Ended March 31,
Income (Loss) Components		(Income (Expense)) in
		Consolidated Statements
		of Operations		2015				2014
Amortization of pension and other post-retirement items
Prior service costs		-1		$	—			$	(87	)
Net loss		-1		(652		)		(132		)
				(652		)		(219		)
		Provision for income taxes		225				84
				(427		)		(135		)
Net unrealized gains on available-for-sale investments
Realized loss on available-for-sale investments		Other income, net		—				(25		)
		Provision for income taxes		—				9
				—				(16		)
Total reclassifications for the period				$	(427	)		$	(151	)
_____________
-1	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 10 (Employee Benefits) to the financial statements included in the 2014 Form 10-K.

Pension_and_PostRetirement_Ben

Pension and Post-Retirement Benefit Costs	3 Months Ended
	Mar. 31, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Pension and Post-Retirement Benefit Costs	Pension and Post-Retirement Benefit Costs
	Defined Benefit Plans
	Components of net periodic benefit cost for the Company's pension plans are as follows:
		Three Months Ended March 31,
		2015					2014
		U.S. Plans			Non-U.S. Plans		U.S. Plans
	Service cost	$	28		$	422	$	84
	Interest cost	544			535		595
	Expected return on plan assets	(819		)	—		(809		)
	Amortization of prior service cost	—			—		74
	Amortization of net loss	290			266		63
	Net periodic benefit cost	$	43		$	1,223	$	7
	The Company made no contribution to the U.S. salaried pension plan in the first three months of 2015. The Company contributed $388 to the U.S. salaried pension plan in the first three months of 2014. The Company contributed $112 and $290 to the U.S. wage pension plan in the first three months of 2015 and 2014, respectively. The Company's funding policy for its U.S. plans is consistent with the minimum funding requirements of federal law and regulations, and based on preliminary estimates, the Company expects to make no contribution for the salaried pension plan and additional contributions of approximately $237 to the wage pension plan during the fiscal year ending December 31, 2015.
	Other Post-retirement Benefits
	Components of net periodic benefit cost for the Company's other post-retirement benefits are as follows:
		Three Months Ended March 31,
		2015			2014
		U.S. Plans			U.S. Plans
	Service cost	$	6		$	5
	Interest cost	149			181
	Amortization of prior service cost	—			13
	Amortization of net loss	96			69
	Net periodic benefit cost	$	251		$	268

StockBased_Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation
	Under the Westlake Chemical Corporation 2013 Omnibus Incentive Plan (as amended and restated, the "2013 Plan"), all employees and non-employee directors of the Company, as well as certain individuals who have agreed to become the Company's employees, are eligible for awards. Shares of common stock may be issued as authorized in the 2013 Plan. At the discretion of the administrator of the 2013 Plan, employees and non-employee directors may be granted awards in the form of stock options, stock appreciation rights, stock awards, restricted stock units or cash awards (any of which may be a performance award). Total stock-based compensation expense related to the 2013 Plan was $2,340 and $2,222 for the three months ended March 31, 2015 and 2014, respectively.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments
	Commodity Risk Management
	The Company uses derivative instruments to reduce price volatility risk on raw materials and products as a substantial portion of its raw materials and products are commodities whose prices fluctuate as market supply and demand fundamentals change. Business strategies to protect against such instability include ethylene product feedstock flexibility and moving downstream into the olefins and vinyls products where pricing is more stable. The Company does not use derivative instruments to engage in speculative activities.
	For derivative instruments that are designated and qualify as fair value hedges, the gains or losses on the derivative instruments, as well as the offsetting losses or gains on the hedged items attributable to the hedged risk, are included in cost of sales in the consolidated statement of operations. The Company had no derivative instruments that were designated as fair value hedges for the three months ended March 31, 2015 and 2014.
	Gains and losses from changes in the fair value of derivative instruments that are not designated as hedging instruments were included in gross profit in the consolidated statements of operations for the three months ended March 31, 2015 and 2014.
	The exposure on commodity derivatives used for price risk management includes the risk that the counterparty will not pay if the market declines below the established fixed price. In such case, the Company would lose the benefit of the derivative differential on the volume of the commodities covered. In any event, the Company would continue to receive the market price on the actual volume hedged. The Company also bears the risk that it could lose the benefit of market improvements over the fixed derivative price for the term and volume of the derivative instruments (as such improvements would accrue to the benefit of the counterparty).
	Disclosures related to the Company's derivative assets and derivative liabilities subject to enforceable master netting arrangements have not been presented as they are not material to the Company's consolidated balance sheets at March 31, 2015 and December 31, 2014.
	The fair values of derivative instruments in the Company's consolidated balance sheets were as follows:
		Derivative Assets
		Balance Sheet Location	Fair Value as of
			March 31,		December 31,
			2015		2014
	Not designated as hedging instruments
	Commodity forward contracts	Accounts receivable, net	$	2,927	$	3,145
	Commodity forward contracts	Deferred charges and	1,557		—
		other assets, net
	Total derivative assets		$	4,484	$	3,145
		Derivative Liabilities
		Balance Sheet Location	Fair Value as of
			March 31,		December 31,
			2015		2014
	Not designated as hedging instruments
	Commodity forward contracts	Accrued liabilities	$	5,060	$	6,549
	Commodity forward contracts	Other liabilities	1,801		3,559
	Total derivative liabilities		$	6,861	$	10,108
	The impact of derivative instruments that have not been designated as hedges on the Company's consolidated statements of operations were as follows:
	Derivatives Not Designated as	Location of Gain (Loss)	Three Months Ended March 31,
	Hedging Instruments	Recognized in
		Income on Derivative	2015		2014
	Commodity forward contracts	Gross profit	$	4,241	$	(611	)
	See Note 12 for the fair value of the Company's derivative instruments.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	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 following tables summarize, by level within the fair value hierarchy, the Company's assets and liabilities that were accounted for at fair value on a recurring basis:
		31-Mar-15
		Level 1			Level 2			Total
	Derivative instruments
	Risk management assets—Commodity forward contracts	$	4,209		$	275		$	4,484
	Risk management liabilities—Commodity forward contracts	(17		)	(6,844		)	(6,861		)
	Marketable securities
	Available-for-sale securities	17,033			—			17,033
		December 31, 2014
		Level 1			Level 2			Total
	Derivative instruments
	Risk management assets—Commodity forward contracts	$	3,143		$	2		$	3,145
	Risk management liabilities—Commodity forward contracts	—			(10,108		)	(10,108		)
	Marketable securities
	Available-for-sale securities	15,414			—			15,414
	The Level 2 measurements for the Company's commodity contracts are derived using forward curves supplied by industry-recognized and unrelated third-party services.
	There were no transfers in or out of Levels 1 and 2 of the fair value hierarchy for the three months ended March 31, 2015 and 2014.
	In addition to the financial assets and liabilities above, the Company has other 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 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.
		31-Mar-15						December 31, 2014
		Carrying			Fair			Carrying			Fair
		Value			Value			Value			Value
	3.60% senior notes due 2022	$	249,138		$	253,240		$	249,108		$	248,630
	6 ½% senior notes due 2029	100,000			118,493			100,000			116,384
	6 ¾% senior notes due 2032	250,000			280,285			250,000			285,545
	6 ½% GO Zone Senior Notes Due 2035	89,000			105,298			89,000			106,504
	6 ½% IKE Zone Senior Notes Due 2035	65,000			76,903			65,000			77,784
	Loan related to tax-exempt waste disposal revenue	10,889			10,889			10,889			10,889
	bonds due 2027

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	The effective income tax rate was 34.3% for the three months ended March 31, 2015. The effective income tax rate for the 2015 period was below the U.S. federal statutory rate of 35.0% primarily due to the benefit of state tax credits, the domestic manufacturing deduction, income attributable to noncontrolling interests and the foreign earnings rate differential, partially offset by state income taxes. The effective income tax rate was 34.5% for the three months ended March 31, 2014. The effective income tax rate for the 2014 period was below the U.S. federal statutory rate of 35.0% primarily due to state tax credits and the domestic manufacturing deduction, mostly offset by state income taxes.
	There were no unrecognized tax benefits for the three months ended March 31, 2015. The Company recognizes penalties and interest accrued related to unrecognized tax benefits in income tax expense. As of March 31, 2015, the Company had no accrued interest and penalties related to uncertain tax positions.
	The Company files income tax returns in the U.S. federal jurisdiction, various states and foreign jurisdictions. The Company is no longer subject to examinations by tax authorities before the year 2008.

Earnings_per_Share

Earnings per Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share
	The Company has unvested shares of restricted stock and 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 include the effect of certain stock options.
		Three Months Ended March 31,
		2015			2014
	Net income attributable to Westlake Chemical Corporation	$	146,342		$	158,032
	Less:
	Net income attributable to participating securities	(200		)	(384		)
	Net income attributable to common shareholders	$	146,142		$	157,648
	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 March 31,
		2015			2014
	Weighted average common shares—basic	132,714,566			133,072,254
	Plus incremental shares from:
	Assumed exercise of options	490,740			540,670
	Weighted average common shares—diluted	133,205,306			133,612,924
	Earnings per common share attributable to Westlake Chemical Corporation :
	Basic	$	1.1		$	1.18
	Diluted	$	1.1		$	1.18
	Excluded from the computation of diluted earnings per share are options to purchase 241,312 and 69,662 shares of common stock for the three months ended March 31, 2015 and 2014, respectively. These options were outstanding during the periods reported but were excluded because the effect of including them would have been antidilutive.

Supplemental_Information

Supplemental Information	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information
	Other Liabilities
	Other liabilities were $157,130 and $174,859 at March 31, 2015 and December 31, 2014, respectively. Non-current pension obligation, which is a component of other liabilities, was $123,207 and $136,296 at March 31, 2015 and December 31, 2014, respectively. No other component of other liabilities was more than five percent of total liabilities.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	The Company is subject to environmental laws and regulations that can impose civil and criminal sanctions and that may require it to mitigate the effects of contamination caused by the release or disposal of hazardous substances into the environment. Under one law, the U.S. Comprehensive Environmental Response, Compensation, and Liability Act ("CERCLA"), an owner or operator of property may be held strictly liable for remediating contamination without regard to whether that person caused the contamination, and without regard to whether the practices that resulted in the contamination were legal at the time they occurred. Because several of the Company's production sites have a history of industrial use, it is impossible to predict precisely what effect these legal requirements will have on the Company.
	European Regulations. Under the Industrial Emission Directive ("IED"), European Union member state governments are expected to adopt rules and implement environmental permitting programs relating to air, water and waste for industrial facilities. In this context, concepts such as BAT ("best available technique") are being explored. Future implementation of these concepts may result in technical modifications in the Company's European facilities. In addition, under the Environmental Liability Directive, European Union member states can require the remediation of soil and groundwater contamination in certain circumstances, under the "polluter pays principle." The Company is unable to predict the impact these requirements and concepts may have on its future costs of compliance.
	Contract Disputes with Goodrich and PolyOne. In connection with the 1990 and 1997 acquisitions of the Goodrich Corporation ("Goodrich") chemical manufacturing facility in Calvert City, Kentucky, Goodrich agreed to indemnify the Company for any liabilities related to preexisting contamination at the site. 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 site, which does not include the Company's nearby polyvinyl chloride ("PVC") facility, had been extensively contaminated under Goodrich's operations. In 1993, Goodrich spun off the predecessor of PolyOne Corporation ("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; (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; and (3) the Company and PolyOne would negotiate a new environmental remediation utilities and services agreement to cover the Company's provision to, or on behalf of, PolyOne of certain environmental remediation services at the site. The current environmental remediation activities at the Calvert City site do not have a specified termination date but are expected to last for the foreseeable future. The costs incurred by the Company that have been invoiced to PolyOne to provide the environmental remediation services were $2,805 in 2014. By letter dated March 16, 2010, PolyOne notified the Company that it was initiating an arbitration proceeding under the settlement agreement. In this proceeding, PolyOne seeks to readjust the percentage allocation of costs and to recover approximately $1,400 from the Company in reimbursement of previously paid remediation costs. The arbitration is currently stayed.
	State Administrative Proceedings. There are several administrative proceedings in Kentucky involving the Company, Goodrich and PolyOne related to the same manufacturing site in Calvert City. In 2003, the Kentucky Environmental and Public Protection Cabinet (the "Cabinet") re-issued Goodrich's Resource Conservation and Recovery Act ("RCRA") permit which requires Goodrich to remediate contamination at the Calvert City manufacturing site. Both Goodrich and PolyOne challenged various terms of the permit in an attempt to shift Goodrich's clean-up obligations under the permit to the Company. The Company intervened in the proceedings. The Cabinet has suspended all corrective action under the RCRA permit in deference to a remedial investigation and feasibility study ("RIFS") being conducted, under the auspices of the U.S. Environmental Protection Agency ("EPA"), pursuant to an Administrative Settlement Agreement ("AOC"), which became effective on December 9, 2009. See "Federal Administrative Proceedings" below. The proceedings have been postponed. Periodic status conferences will be held to evaluate whether additional proceedings will be required.
	Federal Administrative Proceedings. In May 2009, the Cabinet sent a letter to the EPA requesting the EPA's assistance in addressing contamination at the Calvert City site under CERCLA. In its response to the Cabinet also in May 2009, the EPA stated that it concurred with the Cabinet's request and would incorporate work previously conducted under the Cabinet's RCRA authority into the EPA's cleanup efforts under CERCLA. Since 1983, the EPA has been addressing contamination at an abandoned landfill adjacent to the Company's plant which had been operated by Goodrich and which was being remediated pursuant to CERCLA. The EPA has directed Goodrich and PolyOne to conduct additional investigation activities at the landfill and at the Company's plant. In June 2009, the EPA notified the Company that the Company may have potential liability under section 107(a) of CERCLA at its plant site. Liability under section 107(a) of CERCLA is strict and joint and several. The EPA also identified Goodrich and PolyOne, among others, as potentially responsible parties at the plant site. The Company negotiated, in conjunction with the other potentially responsible parties, an AOC and an order to conduct a RIFS. On July 12, 2013, the parties submitted separate draft RIFS reports to the EPA. The EPA has hired a contractor to complete the remedial investigation report.
	Monetary Relief. Except as noted above with respect to the settlement of the contract litigation among the Company, Goodrich and PolyOne, none of the court, the Cabinet nor the EPA has established any allocation of the costs of remediation among the various parties that are involved in the judicial and administrative proceedings discussed above. At this time, the Company is not able to estimate the loss or reasonable possible loss, if any, on the Company's financial statements that could result from the resolution of these proceedings. Any cash expenditures that the Company might incur in the future with respect to the remediation of contamination at the site 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.
	Potential Flare Modifications. For several years, the EPA has been conducting an enforcement initiative against petroleum refineries and petrochemical plants with respect to emissions from flares. A number of companies have entered into consent agreements with the EPA requiring both modifications to reduce flare emissions and the installation of additional equipment to better track flare operations and emissions. On April 21, 2014, the Company received a Clean Air Act Section 114 Information Request from the EPA which sought information regarding flares at the Calvert City and Lake Charles, Louisiana facilities. The EPA has informed the Company that the information provided leads the EPA to believe that some of the flares are out of compliance with applicable standards. The EPA has demanded that the Company conduct additional flare sampling and provide supplemental information. The Company is currently in negotiations with the EPA regarding these demands. The EPA has indicated that it is seeking a consent decree that would obligate the Company to take corrective actions relating to the alleged noncompliance. The Company has not agreed that any flares are out of compliance or that any corrective actions are warranted. Depending on the outcome of the Company's negotiations with the EPA, additional controls on emissions from its flares may be required and these could result in increased capital and operating costs.
	Louisiana Notice of Violations. The Louisiana Department of Environmental Quality ("LDEQ") has issued notices of violations ("NOVs") regarding the Company's assets for various air compliance issues. The Company is working with LDEQ to settle these claims, and a global settlement of all claims is being discussed. Such global settlement may result in a total civil penalty of approximately $200.
	In addition to the matters described above, the Company is involved in various legal proceedings incidental to the conduct of its business. The Company does not believe that any of these legal proceedings will have a material adverse effect on its financial condition, results of operations or cash flows.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	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 March 31,
		2015			2014
	Net external sales
	Olefins
	Polyethylene	$	409,432		$	487,144
	Styrene, feedstock and other	173,645			235,654
	Total Olefins	583,077			722,798
	Vinyls
	PVC, caustic soda and other	416,988			190,527
	Building products	103,466			114,351
	Total Vinyls	520,454			304,878
		$	1,103,531		$	1,027,676
	Intersegment sales
	Olefins	$	23,462		$	56,853
	Vinyls	370			343
		$	23,832		$	57,196
	Income (loss) from operations
	Olefins	$	191,103		$	272,333
	Vinyls	47,086			(21,114		)
	Corporate and other	(8,909		)	(3,164		)
		$	229,280		$	248,055
	Depreciation and amortization
	Olefins	$	26,939		$	26,647
	Vinyls	31,584			19,168
	Corporate and other	118			157
		$	58,641		$	45,972
	Other income (expense), net
	Olefins	$	2,552		$	1,454
	Vinyls	5,503			(34		)
	Corporate and other	1,041			1,089
		$	9,096		$	2,509
	Provision for (benefit from) income taxes
	Olefins	$	66,457		$	93,550
	Vinyls	12,805			(10,070		)
	Corporate and other	(884		)	(105		)
		$	78,378		$	83,375
	Capital expenditures
	Olefins	$	55,300		$	29,074
	Vinyls	36,855			81,120
	Corporate and other	3,667			547
		$	95,822		$	110,741
	A reconciliation of total segment income from operations to consolidated income before income taxes is as follows:
		Three Months Ended March 31,
		2015			2014
	Income from operations	$	229,280		$	248,055
	Interest expense	(9,591		)	(9,157		)
	Other income, net	9,096			2,509
	Income before income taxes	$	228,785		$	241,407
		March 31,			December 31,
		2015			2014
	Total assets
	Olefins	$	1,783,845		$	1,785,895
	Vinyls	2,510,470			2,618,646
	Corporate and other	885,470			809,449
		$	5,179,785		$	5,213,990

Subsequent_Events

Subsequent Events	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events
	On April 29, 2015, Westlake Chemical Partners LP ("Westlake Partners") purchased an additional 2.7% newly issued limited partner interest in OpCo for approximately $135,341, resulting in Westlake Partners holding approximately an aggregate 13.3% limited partner interest in OpCo and the Company holding approximately an aggregate 86.7% limited partner interest in OpCo. In order to fund this purchase, Westlake Partners entered into a revolving credit facility with a subsidiary of the Company, which has a total borrowing capacity of $300,000.
	Subsequent events were evaluated through the date on which the financial statements were issued.

Guarantor_Disclosures

Guarantor Disclosures	3 Months Ended
	Mar. 31, 2015
Guarantees [Abstract]
Guarantor Disclosures	Guarantor Disclosures
	The Company's payment obligations under the 3.60% senior notes due 2022 are fully and unconditionally guaranteed by each of its current and future domestic subsidiaries that guarantee other debt of the Company or of another guarantor of the 3.60% senior notes due 2022 in excess of $5,000 (the "Guarantor Subsidiaries"). Except for Westlake Chemical OpCo LP ("OpCo"), which is less than 100% owned, each Guarantor Subsidiary is 100% owned by Westlake Chemical Corporation (the "100% Owned Guarantor Subsidiaries"). The August 4, 2014 initial public offering of Westlake Chemical Partners LP ("Westlake Partners") resulted in OpCo ceasing to be a 100% owned subsidiary of the Company. OpCo has been presented as a less than 100% owned guarantor subsidiary in each of the tables below, including for periods prior to the initial public offering of Westlake Partners. These guarantees are the joint and several obligations of the Guarantor Subsidiaries. The following unaudited condensed consolidating financial information presents the financial condition, results of operations and cash flows of Westlake Chemical Corporation, the 100% owned Guarantor Subsidiaries, OpCo and the remaining subsidiaries that do not guarantee the 3.60% senior notes due 2022 (the "Non-Guarantor Subsidiaries"), together with consolidating eliminations necessary to present the Company's results on a consolidated basis.
	Condensed Consolidating Financial Information as of March 31, 2015
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Balance Sheet
	Current assets
	Cash and cash equivalents	$	701,622		$	2,606		$	143,005		$	98,416		$	—		$	945,649
	Accounts receivable, net	11,605			1,497,572			54,979			128,116			(1,165,145		)	527,127
	Inventories	—			395,664			4,564			80,152			—			480,380
	Prepaid expenses and other current assets	92			18,236			122			2,160			(2,592		)	18,018
	Deferred income taxes	409			29,832			—			747			—			30,988
	Total current assets	713,728			1,943,910			202,670			309,591			(1,167,737		)	2,002,162
	Property, plant and equipment, net	—			1,500,234			866,546			384,706			—			2,751,486
	Equity investments	4,123,427			1,232,093			—			351,048			(5,641,847		)	64,721
	Other assets, net	31,209			415,180			53,832			124,633			(263,438		)	361,416
	Total assets	$	4,868,364		$	5,091,417		$	1,123,048		$	1,169,978		$	(7,073,022	)	$	5,179,785
	Current liabilities
	Accounts payable	$	1,118,864		$	153,645		$	27,395		$	89,383		$	(1,141,794	)	$	247,493
	Accrued liabilities	16,504			150,074			6,104			58,975			(25,943		)	205,714
	Total current liabilities	1,135,368			303,719			33,499			148,358			(1,167,737		)	453,207
	Long-term debt	753,138			10,889			257,829			—			(257,829		)	764,027
	Deferred income taxes	—			503,540			1,902			34,846			(5,609		)	534,679
	Other liabilities	—			38,625			—			118,505			—			157,130
	Total liabilities	1,888,506			856,773			293,230			301,709			(1,431,175		)	1,909,043
	Total Westlake Chemical Corporation stockholders' equity	2,979,858			4,234,644			829,818			577,385			(5,641,847		)	2,979,858
	Noncontrolling interests	—			—			—			290,884			—			290,884
	Total equity	2,979,858			4,234,644			829,818			868,269			(5,641,847		)	3,270,742
	Total liabilities and equity	$	4,868,364		$	5,091,417		$	1,123,048		$	1,169,978		$	(7,073,022	)	$	5,179,785
	Condensed Consolidating Financial Information as of December 31, 2014
		Westlake			100% Owned			OpCo			Non-Guarantor			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Subsidiaries
		Corporation			Subsidiaries			100% Owned
								Guarantor
								Subsidiary)
	Balance Sheet
	Current assets
	Cash and cash equivalents	$	655,947		$	3,057		$	131,545		$	90,052		$	—		$	880,601
	Accounts receivable, net	8,451			1,454,709			56,049			135,133			(1,093,676		)	560,666
	Inventories	—			414,975			6,634			104,167			—			525,776
	Prepaid expenses and other current assets	172			9,485			212			1,938			—			11,807
	Deferred income taxes	409			29,832			—			2,196			—			32,437
	Total current assets	664,979			1,912,058			194,440			333,486			(1,093,676		)	2,011,287
	Property, plant and equipment, net	—			1,477,515			842,057			437,985			—			2,757,557
	Equity investments	4,033,378			1,237,080			—			352,550			(5,561,703		)	61,305
	Other assets, net	30,543			387,325			57,733			141,948			(233,708		)	383,841
	Total assets	$	4,728,900		$	5,013,978		$	1,094,230		$	1,265,969		$	(6,889,087	)	$	5,213,990
	Current liabilities
	Accounts payable	$	1,055,527		$	160,834		$	17,680		$	95,856		$	(1,068,835	)	$	261,062
	Accrued liabilities	8,754			203,608			11,225			77,372			(24,841		)	276,118
	Total current liabilities	1,064,281			364,442			28,905			173,228			(1,093,676		)	537,180
	Long-term debt	753,108			10,889			227,638			—			(227,638		)	763,997
	Deferred income taxes	—			497,919			1,848			42,369			(6,070		)	536,066
	Other liabilities	—			43,452			—			131,407			—			174,859
	Total liabilities	1,817,389			916,702			258,391			347,004			(1,327,384		)	2,012,102
	Total Westlake Chemical Corporation stockholders' equity	2,911,511			4,097,276			835,839			628,588			(5,561,703		)	2,911,511
	Noncontrolling interests	—			—			—			290,377			—			290,377
	Total equity	2,911,511			4,097,276			835,839			918,965			(5,561,703		)	3,201,888
	Total liabilities and equity	$	4,728,900		$	5,013,978		$	1,094,230		$	1,265,969		$	(6,889,087	)	$	5,213,990
	Condensed Consolidating Financial Information for the Three Months Ended March 31, 2015
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
Chemical			Guarantor			(Less Than			Guarantor
Corporation			Subsidiaries			100% Owned			Subsidiaries
						Guarantor
						Subsidiary)
Statement of Operations
Net sales	$	—		$	903,492		$	258,391		$	245,643		$	(303,995	)	$	1,103,531
Cost of sales	—			727,399			162,164			228,269			(298,847		)	818,985
Gross profit	—			176,093			96,227			17,374			(5,148		)	284,546
Selling, general and administrative expenses	413			43,684			5,046			11,271			(5,148		)	55,266
(Loss) income from operations	(413		)	132,409			91,181			6,103			—			229,280
Interest expense	(10,752		)	(1		)	(1,376		)	(42		)	2,580			(9,591		)
Other income, net	6,612			2,827			5			2,232			(2,580		)	9,096
(Loss) income before income taxes	(4,553		)	135,235			89,810			8,293			—			228,785
(Benefit from) provision for income taxes	(1,578		)	77,999			467			1,490			—			78,378
Equity in net income of subsidiaries	149,317			79,891			—			9,452			(238,660		)	—
Net income	146,342			137,127			89,343			16,255			(238,660		)	150,407
Net income attributable to noncontrolling interests	—			—			—			4,065			—			4,065
Net income attributable to Westlake Chemical Corporation	$	146,342		$	137,127		$	89,343		$	12,190		$	(238,660	)	$	146,342
Comprehensive income (loss) attributable to Westlake Chemical	$	88,113		$	137,365		$	89,343		$	(47,319	)	$	(179,389	)	$	88,113
Corporation
Condensed Consolidating Financial Information for the Three Months Ended March 31, 2014
	Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
	Chemical			Guarantor			(Less Than			Guarantor
	Corporation			Subsidiaries			100% Owned			Subsidiaries
							Guarantor
							Subsidiary)
Statement of Operations
Net sales	$	—		$	844,342		$	560,014		$	9,117		$	(385,797	)	$	1,027,676
Cost of sales	—			790,577			327,700			8,186			(385,797		)	740,666
Gross profit	—			53,765			232,314			931			—			287,010
Selling, general and administrative expenses	546			29,285			7,778			1,346			—			38,955
(Loss) income from operations	(546		)	24,480			224,536			(415		)	—			248,055
Interest expense	(8,947		)	(210		)	(3,591		)	—			3,591			(9,157		)
Other income (expense), net	5,006			456			1,252			(614		)	(3,591		)	2,509
(Loss) income before income taxes	(4,487		)	24,726			222,197			(1,029		)	—			241,407
(Benefit from) provision for income taxes	(1,558		)	6,787			78,323			(177		)	—			83,375
Equity in net income of subsidiaries	160,961			143,874			—			—			(304,835		)	—
Net income (loss) attributable to Westlake Chemical Corporation	$	158,032		$	161,813		$	143,874		$	(852	)	$	(304,835	)	$	158,032
Comprehensive income (loss) attributable to Westlake Chemical	$	158,866		$	161,948		$	143,874		$	(1,750	)	$	(304,072	)	$	158,866
Corporation
Condensed Consolidating Financial Information for the Three Months Ended March 31, 2015
	Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
	Chemical			Guarantor			(Less Than			Guarantor
	Corporation			Subsidiaries			100% Owned			Subsidiaries
							Guarantor
							Subsidiary)
Statement of Cash Flows
Cash flows from operating activities
Net income	$	146,342		$	137,127		$	89,343		$	16,255		$	(238,660	)	$	150,407
Adjustments to reconcile net income to net cash (used for)
provided by operating activities
Depreciation and amortization	501			29,592			19,803			9,246			—			59,142
Deferred income taxes	(124		)	6,431			54			(1,030		)	—			5,331
Net changes in working capital and other	(151,572		)	(114,779		)	6,973			(3,606		)	238,660			(24,324		)
Net cash (used for) provided by operating activities	(4,853		)	58,371			116,173			20,865			—			190,556
Cash flows from investing activities
Additions to property, plant and equipment	—			(47,385		)	(39,540		)	(8,897		)	—			(95,822		)
Settlements of derivative instruments	—			(833		)	—			—			—			(833		)
Net cash used for investing activities	—			(48,218		)	(39,540		)	(8,897		)	—			(96,655		)
Cash flows from financing activities
Intercompany financing	72,634			(99,765		)	30,191			(3,060		)	—			—
Dividends paid	(21,964		)	—			—			—			—			(21,964		)
Distributions paid	—			89,161			(95,364		)	2,645			—			(3,558		)
Proceeds from exercise of stock options	157			—			—			—			—			157
Repurchase of common stock for treasury	(2,000		)	—			—			—			—			(2,000		)
Windfall tax benefits from share-based payment arrangements	1,701			—			—			—			—			1,701
Net cash provided by (used for) financing activities	50,528			(10,604		)	(65,173		)	(415		)	—			(25,664		)
Effect of exchange rate changes on cash and cash equivalents	—			—			—			(3,189		)	—			(3,189		)
Net increase (decrease) in cash and cash equivalents	45,675			(451		)	11,460			8,364			—			65,048
Cash and cash equivalents at beginning of period	655,947			3,057			131,545			90,052			—			880,601
Cash and cash equivalents at end of period	$	701,622		$	2,606		$	143,005		$	98,416		$	—		$	945,649
Condensed Consolidating Financial Information for the Three Months Ended March 31, 2014
	Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
	Chemical			Guarantor			(Less Than			Guarantor
	Corporation			Subsidiaries			100% Owned			Subsidiaries
							Guarantor
							Subsidiary)
Statement of Cash Flows
Cash flows from operating activities
Net income (loss)	$	158,032		$	161,813		$	143,874		$	(852	)	$	(304,835	)	$	158,032
Adjustments to reconcile net income (loss) to net cash (used for)
provided by operating activities
Depreciation and amortization	365			26,394			19,014			564			—			46,337
Deferred income taxes	(162		)	5,220			3,267			(50		)	—			8,275
Net changes in working capital and other	(165,553		)	(169,342		)	31,731			(1,810		)	304,835			(139		)
Net cash (used for) provided by operating activities	(7,318		)	24,085			197,886			(2,148		)	—			212,505
Cash flows from investing activities
Additions to property, plant and equipment	—			(59,254		)	(51,305		)	(182		)	—			(110,741		)
Proceeds from disposition of assets	—			12			—			—			—			12
Proceeds from sales and maturities of securities	30,119			—			—			—			—			30,119
Purchase of securities	(49,025		)	—			—			—			—			(49,025		)
Settlements of derivative instruments	—			—			(409		)	—			—			(409		)
Net cash used for investing activities	(18,906		)	(59,242		)	(51,714		)	(182		)	—			(130,044		)
Cash flows from financing activities
Intercompany financing	106,903			(155,387		)	46,041			2,443			—			—
Net distributions prior to Westlake Partners initial public offering	—			192,213			(192,213		)	—			—			—
Dividends paid	(16,789		)	—			—			—			—			(16,789		)
Proceeds from exercise of stock options	2,158			—			—			—			—			2,158
Windfall tax benefits from share-based payment arrangements	3,512			—			—			—			—			3,512
Net cash provided by (used for) financing activities	95,784			36,826			(146,172		)	2,443			—			(11,119		)
Net increase in cash and cash equivalents	69,560			1,669			—			113			—			71,342
Cash and cash equivalents at beginning of period	420,948			6,227			—			34,126			—			461,301
Cash and cash equivalents at end of period	$	490,508		$	7,896		$	—		$	34,239		$	—		$	532,643

Basis_of_Financial_Statements_

Basis of Financial Statements (Policies)	3 Months Ended
	Mar. 31, 2015
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, 2014 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, 2014 (the "2014 Form 10-K"), filed with the SEC on February 25, 2015. These 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, 2014.
	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 March 31, 2015, its results of operations for the three months ended March 31, 2015 and 2014 and the changes in its cash position for the three months ended March 31, 2015 and 2014.
	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, 2015 or any other interim period. The preparation of 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	Revenue from Contracts with Customers
	In May 2014, the Financial Accounting Standards Board ("FASB") issued an accounting standards update on a comprehensive new revenue recognition standard that will supersede the existing 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 will be 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 either "full retrospective" adoption, meaning that the standard is applied to all of the periods presented with a cumulative catch-up as of the earliest period presented, or "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 accounting standard will be effective for reporting periods beginning after December 15, 2016. The Company is in the process of evaluating the impact that the new accounting guidance will have on its consolidated financial position, results of operations and cash flows.
	Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items
	In January 2015, the FASB issued an accounting standards update to simplify income statement classification by removing the concept of extraordinary items from U.S. GAAP. Under the new standard, an unusual and infrequent event or transaction is no longer allowed to be separately disclosed as "extraordinary." The standard retains the existing requirement to separately present items that are of an unusual nature or occur infrequently on a pre-tax basis within income from continuing operations. The new guidance also requires similar separate presentation of items that are both unusual and infrequent on a pre-tax basis within income from continuing operations. The standard allows for either prospective or retrospective application. If adopted prospectively, both the nature and amount of any subsequent adjustments to previously reported extraordinary items must be disclosed. The accounting standard will be effective for reporting periods beginning after December 15, 2015 and is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows.

Financial_Instruments_Tables

Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Investments in available-for-sale securities were classified as follows:
		March 31,			December 31,
		2015			2014
	Non-current	$	17,033		$	15,414
	Total available-for-sale securities	$	17,033		$	15,414
Available-for-sale Securities	The cost, gross unrealized gains, gross unrealized losses and fair value of the Company's available-for-sale securities were as follows:
			March 31, 2015
			Cost			Gross			Gross		Fair Value
						Unrealized			Unrealized
						Gains			Losses
	Equity securities		$	15,043		$	1,990		$	—	$	17,033
	Total available-for-sale securities		$	15,043		$	1,990		$	—	$	17,033
			December 31, 2014
			Cost			Gross			Gross		Fair Value
						Unrealized			Unrealized
						Gains			Losses
	Equity securities		$	15,050		$	364		$	—	$	15,414
	Total available-for-sale securities		$	15,050		$	364		$	—	$	15,414
Schedule of Realized Gain (Loss)
			Three Months Ended March 31,
			2015			2014
	Proceeds from sales and maturities of securities		$	—		$	30,119
	Gross realized gains		—			13
	Gross realized losses		—			(38		)

Accounts_Receivable_Tables

Accounts Receivable (Tables)	3 Months Ended
	Mar. 31, 2015
Accounts Receivable, Net [Abstract]
Schedule Of Accounts Receivable	Accounts receivable consist of the following:
		March 31,			December 31,
		2015			2014
	Trade customers	$	500,262		$	525,546
	Affiliates	449			437
	Allowance for doubtful accounts	(13,259		)	(13,468		)
		487,452			512,515
	Federal and state taxes	21,289			8,919
	Other	18,386			39,232
	Accounts receivable, net	$	527,127		$	560,666

Inventories_Tables

Inventories (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following:
		March 31,		December 31,
		2015		2014
	Finished products	$	278,501	$	300,909
	Feedstock, additives and chemicals	135,903		158,635
	Materials and supplies	65,976		66,232
	Inventories	$	480,380	$	525,776

LongTerm_Debt_Tables

Long-Term Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	Long-term debt consists of the following:
		March 31,		December 31,
		2015		2014
	3.60% senior notes due 2022	$	249,138	$	249,108
	6 ½% senior notes due 2029	100,000		100,000
	6 ¾% senior notes due 2032	250,000		250,000
	6 ½% senior notes due 2035 (the "6 ½% GO Zone Senior Notes Due 2035")	89,000		89,000
	6 ½% senior notes due 2035 (the "6 ½% IKE Zone Senior Notes Due 2035")	65,000		65,000
	Loan related to tax-exempt waste disposal revenue bonds due 2027	10,889		10,889
	Long-term debt, net	$	764,027	$	763,997

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Schedule of Stockholders Equity	Changes in stockholders' equity for the three months ended March 31, 2015 and 2014 were as follows:
			Common				Common				Additional		Retained			Accumulated Other Comprehensive			Noncontrolling Interests			Total
			Stock				Stock,				Paid-in		Earnings			Income (Loss)
							Held in				Capital
							Treasury
	Balances at December 31, 2014		$	1,347			$	(96,372	)		$	530,441	$	2,555,528		$	(79,433	)	$	290,377		$	3,201,888
	Net income		—				—				—		146,342			—			4,065			150,407
	Other comprehensive income
	(loss), net of income taxes:
	Pension and other post-		—				—				—		—			427			—			427
	retirement benefits
	liability
	Foreign currency		—				—				—		—			(59,698		)	—			(59,698		)
	translation adjustments
	Net unrealized holding		—				—				—		—			1,042			—			1,042
	gains on investments
	Common stock repurchased		—				(2,000		)		—		—			—			—			(2,000		)
	Shares issued—stock-		—				97				60		—			—			—			157
	based compensation
	Stock-based compensation,		—				—				4,041		—			—			—			4,041
	net of tax on stock options
	exercised
	Dividends paid		—				—				—		(21,964		)	—			—			(21,964		)
	Distributions to noncontrolling		—				—				—		—			—			(3,558		)	(3,558		)
	interests
	Balances at March 31, 2015		$	1,347			$	(98,275	)		$	534,542	$	2,679,906		$	(137,662	)	$	290,884		$	3,270,742
			Common				Common				Additional		Retained			Accumulated Other Comprehensive			Total
			Stock				Stock,				Paid-in		Earnings			Income (Loss)
							Held in				Capital
							Treasury
	Balances at December 31, 2013		$	1,346			$	(46,220	)		$	511,432	$	1,954,661		$	(2,616	)	$	2,418,603
	Net income		—				—				—		158,032			—			158,032
	Other comprehensive income (loss), net of
	income taxes:
	Pension and other post-retirement benefits		—				—				—		—			135			135
	liability
	Foreign currency translation adjustments		—				—				—		—			(898		)	(898		)
	Net unrealized holding gains on		—				—				—		—			1,597			1,597
	investments
	Shares issued—stock-based compensation		1				—				2,157		—			—			2,158
	Stock-based compensation, net of tax on stock		—				—				5,734		—			—			5,734
	options exercised
	Dividends paid		—				—				—		(16,789		)	—			(16,789		)
	Balances at March 31, 2014		$	1,347			$	(46,220	)		$	519,323	$	2,095,904		$	(1,782	)	$	2,568,572
Schedule of Accumulated Other Comprehensive Loss	Changes in accumulated other comprehensive income (loss) by component for the three months ended March 31, 2015 and 2014 were as follows:
			Benefits				Cumulative				Net Unrealized		Total
			Liability,				Foreign				Holding Gains
			Net of Tax				Currency				on Investments,
							Exchange				Net of Tax
	Balances at December 31, 2014		$	(23,442	)		$	(56,224	)		$	233	$	(79,433	)
	Other comprehensive (loss) income before		—				(59,698		)		1,042		(58,656		)
	reclassifications
	Amounts reclassified from accumulated other		427				—				—		427
	comprehensive loss
	Net other comprehensive income (loss) for the period		427				(59,698		)		1,042		(58,229		)
	Balances at March 31, 2015		$	(23,015	)		$	(115,922	)		$	1,275	$	(137,662	)
			Benefits				Cumulative				Net Unrealized		Total
			Liability,				Foreign				Holding Gains
			Net of Tax				Currency				on Investments,
							Exchange				Net of Tax
	Balances at December 31, 2013		$	(6,696	)		$	3,904			$	176	$	(2,616	)
	Other comprehensive (loss) income before		—				(898		)		1,581		683
	reclassifications
	Amounts reclassified from accumulated other		135				—				16		151
	comprehensive loss
	Net other comprehensive income (loss) for the period		135				(898		)		1,597		834
	Balances at March 31, 2014		$	(6,561	)		$	3,006			$	1,773	$	(1,782	)
Reclassification out of Accumulated Other Comprehensive Income (Loss)	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 months ended March 31, 2015 and 2014:
	Details about Accumulated Other Comprehensive		Location of Reclassification		Three Months Ended March 31,
	Income (Loss) Components		(Income (Expense)) in
			Consolidated Statements
			of Operations		2015				2014
	Amortization of pension and other post-retirement items
	Prior service costs		-1		$	—			$	(87	)
	Net loss		-1		(652		)		(132		)
					(652		)		(219		)
			Provision for income taxes		225				84
					(427		)		(135		)
	Net unrealized gains on available-for-sale investments
	Realized loss on available-for-sale investments		Other income, net		—				(25		)
			Provision for income taxes		—				9
					—				(16		)
	Total reclassifications for the period				$	(427	)		$	(151	)
	_____________
	-1	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 10 (Employee Benefits) to the financial statements included in the 2014 Form 10-K.

Pension_and_PostRetirement_Ben1

Pension and Post-Retirement Benefit Costs (Tables)	3 Months Ended
	Mar. 31, 2015
Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]
Components of Net Periodic Benefit Cost	Components of net periodic benefit cost for the Company's other post-retirement benefits are as follows:
		Three Months Ended March 31,
		2015			2014
		U.S. Plans			U.S. Plans
	Service cost	$	6		$	5
	Interest cost	149			181
	Amortization of prior service cost	—			13
	Amortization of net loss	96			69
	Net periodic benefit cost	$	251		$	268
	Components of net periodic benefit cost for the Company's pension plans are as follows:
		Three Months Ended March 31,
		2015					2014
		U.S. Plans			Non-U.S. Plans		U.S. Plans
	Service cost	$	28		$	422	$	84
	Interest cost	544			535		595
	Expected return on plan assets	(819		)	—		(809		)
	Amortization of prior service cost	—			—		74
	Amortization of net loss	290			266		63
	Net periodic benefit cost	$	43		$	1,223	$	7

Derivative_Instruments_Tables

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Values of Derivatives Instruments in Consolidated Balance Sheets	The fair values of derivative instruments in the Company's consolidated balance sheets were as follows:
		Derivative Assets
		Balance Sheet Location	Fair Value as of
			March 31,		December 31,
			2015		2014
	Not designated as hedging instruments
	Commodity forward contracts	Accounts receivable, net	$	2,927	$	3,145
	Commodity forward contracts	Deferred charges and	1,557		—
		other assets, net
	Total derivative assets		$	4,484	$	3,145
		Derivative Liabilities
		Balance Sheet Location	Fair Value as of
			March 31,		December 31,
			2015		2014
	Not designated as hedging instruments
	Commodity forward contracts	Accrued liabilities	$	5,060	$	6,549
	Commodity forward contracts	Other liabilities	1,801		3,559
	Total derivative liabilities		$	6,861	$	10,108
Impact of Derivative Instruments Not Designated as Fair Value Hedges	The impact of derivative instruments that have not been designated as hedges on the Company's consolidated statements of operations were as follows:
	Derivatives Not Designated as	Location of Gain (Loss)	Three Months Ended March 31,
	Hedging Instruments	Recognized in
		Income on Derivative	2015		2014
	Commodity forward contracts	Gross profit	$	4,241	$	(611	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Summary Of Assets And Liabilities Accounted At Fair Value On A Recurring Basis	The following tables summarize, by level within the fair value hierarchy, the Company's assets and liabilities that were accounted for at fair value on a recurring basis:
		31-Mar-15
		Level 1			Level 2			Total
	Derivative instruments
	Risk management assets—Commodity forward contracts	$	4,209		$	275		$	4,484
	Risk management liabilities—Commodity forward contracts	(17		)	(6,844		)	(6,861		)
	Marketable securities
	Available-for-sale securities	17,033			—			17,033
		December 31, 2014
		Level 1			Level 2			Total
	Derivative instruments
	Risk management assets—Commodity forward contracts	$	3,143		$	2		$	3,145
	Risk management liabilities—Commodity forward contracts	—			(10,108		)	(10,108		)
	Marketable securities
	Available-for-sale securities	15,414			—			15,414
Summary Of Carrying And Fair Values Of Long-Term Debt	The carrying and fair values of the Company's 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.
		31-Mar-15						December 31, 2014
		Carrying			Fair			Carrying			Fair
		Value			Value			Value			Value
	3.60% senior notes due 2022	$	249,138		$	253,240		$	249,108		$	248,630
	6 ½% senior notes due 2029	100,000			118,493			100,000			116,384
	6 ¾% senior notes due 2032	250,000			280,285			250,000			285,545
	6 ½% GO Zone Senior Notes Due 2035	89,000			105,298			89,000			106,504
	6 ½% IKE Zone Senior Notes Due 2035	65,000			76,903			65,000			77,784
	Loan related to tax-exempt waste disposal revenue	10,889			10,889			10,889			10,889
	bonds due 2027

Earnings_per_Share_Tables

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Schedule Of Net Income Attributable To Common Stockholders
		Three Months Ended March 31,
		2015			2014
	Net income attributable to Westlake Chemical Corporation	$	146,342		$	158,032
	Less:
	Net income attributable to participating securities	(200		)	(384		)
	Net income attributable to common shareholders	$	146,142		$	157,648
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 March 31,
		2015			2014
	Weighted average common shares—basic	132,714,566			133,072,254
	Plus incremental shares from:
	Assumed exercise of options	490,740			540,670
	Weighted average common shares—diluted	133,205,306			133,612,924
	Earnings per common share attributable to Westlake Chemical Corporation :
	Basic	$	1.1		$	1.18
	Diluted	$	1.1		$	1.18

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Reporting Information
		Three Months Ended March 31,
		2015			2014
	Net external sales
	Olefins
	Polyethylene	$	409,432		$	487,144
	Styrene, feedstock and other	173,645			235,654
	Total Olefins	583,077			722,798
	Vinyls
	PVC, caustic soda and other	416,988			190,527
	Building products	103,466			114,351
	Total Vinyls	520,454			304,878
		$	1,103,531		$	1,027,676
	Intersegment sales
	Olefins	$	23,462		$	56,853
	Vinyls	370			343
		$	23,832		$	57,196
	Income (loss) from operations
	Olefins	$	191,103		$	272,333
	Vinyls	47,086			(21,114		)
	Corporate and other	(8,909		)	(3,164		)
		$	229,280		$	248,055
	Depreciation and amortization
	Olefins	$	26,939		$	26,647
	Vinyls	31,584			19,168
	Corporate and other	118			157
		$	58,641		$	45,972
	Other income (expense), net
	Olefins	$	2,552		$	1,454
	Vinyls	5,503			(34		)
	Corporate and other	1,041			1,089
		$	9,096		$	2,509
	Provision for (benefit from) income taxes
	Olefins	$	66,457		$	93,550
	Vinyls	12,805			(10,070		)
	Corporate and other	(884		)	(105		)
		$	78,378		$	83,375
	Capital expenditures
	Olefins	$	55,300		$	29,074
	Vinyls	36,855			81,120
	Corporate and other	3,667			547
		$	95,822		$	110,741
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 March 31,
		2015			2014
	Income from operations	$	229,280		$	248,055
	Interest expense	(9,591		)	(9,157		)
	Other income, net	9,096			2,509
	Income before income taxes	$	228,785		$	241,407
Total Assets
		March 31,			December 31,
		2015			2014
	Total assets
	Olefins	$	1,783,845		$	1,785,895
	Vinyls	2,510,470			2,618,646
	Corporate and other	885,470			809,449
		$	5,179,785		$	5,213,990

Guarantor_Disclosures_Tables

Guarantor Disclosures (Tables)	3 Months Ended
	Mar. 31, 2015
Guarantees [Abstract]
Condensed Consolidating Financial Information Balance Sheet	Condensed Consolidating Financial Information as of March 31, 2015
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Balance Sheet
	Current assets
	Cash and cash equivalents	$	701,622		$	2,606		$	143,005		$	98,416		$	—		$	945,649
	Accounts receivable, net	11,605			1,497,572			54,979			128,116			(1,165,145		)	527,127
	Inventories	—			395,664			4,564			80,152			—			480,380
	Prepaid expenses and other current assets	92			18,236			122			2,160			(2,592		)	18,018
	Deferred income taxes	409			29,832			—			747			—			30,988
	Total current assets	713,728			1,943,910			202,670			309,591			(1,167,737		)	2,002,162
	Property, plant and equipment, net	—			1,500,234			866,546			384,706			—			2,751,486
	Equity investments	4,123,427			1,232,093			—			351,048			(5,641,847		)	64,721
	Other assets, net	31,209			415,180			53,832			124,633			(263,438		)	361,416
	Total assets	$	4,868,364		$	5,091,417		$	1,123,048		$	1,169,978		$	(7,073,022	)	$	5,179,785
	Current liabilities
	Accounts payable	$	1,118,864		$	153,645		$	27,395		$	89,383		$	(1,141,794	)	$	247,493
	Accrued liabilities	16,504			150,074			6,104			58,975			(25,943		)	205,714
	Total current liabilities	1,135,368			303,719			33,499			148,358			(1,167,737		)	453,207
	Long-term debt	753,138			10,889			257,829			—			(257,829		)	764,027
	Deferred income taxes	—			503,540			1,902			34,846			(5,609		)	534,679
	Other liabilities	—			38,625			—			118,505			—			157,130
	Total liabilities	1,888,506			856,773			293,230			301,709			(1,431,175		)	1,909,043
	Total Westlake Chemical Corporation stockholders' equity	2,979,858			4,234,644			829,818			577,385			(5,641,847		)	2,979,858
	Noncontrolling interests	—			—			—			290,884			—			290,884
	Total equity	2,979,858			4,234,644			829,818			868,269			(5,641,847		)	3,270,742
	Total liabilities and equity	$	4,868,364		$	5,091,417		$	1,123,048		$	1,169,978		$	(7,073,022	)	$	5,179,785
	Condensed Consolidating Financial Information as of December 31, 2014
		Westlake			100% Owned			OpCo			Non-Guarantor			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Subsidiaries
		Corporation			Subsidiaries			100% Owned
								Guarantor
								Subsidiary)
	Balance Sheet
	Current assets
	Cash and cash equivalents	$	655,947		$	3,057		$	131,545		$	90,052		$	—		$	880,601
	Accounts receivable, net	8,451			1,454,709			56,049			135,133			(1,093,676		)	560,666
	Inventories	—			414,975			6,634			104,167			—			525,776
	Prepaid expenses and other current assets	172			9,485			212			1,938			—			11,807
	Deferred income taxes	409			29,832			—			2,196			—			32,437
	Total current assets	664,979			1,912,058			194,440			333,486			(1,093,676		)	2,011,287
	Property, plant and equipment, net	—			1,477,515			842,057			437,985			—			2,757,557
	Equity investments	4,033,378			1,237,080			—			352,550			(5,561,703		)	61,305
	Other assets, net	30,543			387,325			57,733			141,948			(233,708		)	383,841
	Total assets	$	4,728,900		$	5,013,978		$	1,094,230		$	1,265,969		$	(6,889,087	)	$	5,213,990
	Current liabilities
	Accounts payable	$	1,055,527		$	160,834		$	17,680		$	95,856		$	(1,068,835	)	$	261,062
	Accrued liabilities	8,754			203,608			11,225			77,372			(24,841		)	276,118
	Total current liabilities	1,064,281			364,442			28,905			173,228			(1,093,676		)	537,180
	Long-term debt	753,108			10,889			227,638			—			(227,638		)	763,997
	Deferred income taxes	—			497,919			1,848			42,369			(6,070		)	536,066
	Other liabilities	—			43,452			—			131,407			—			174,859
	Total liabilities	1,817,389			916,702			258,391			347,004			(1,327,384		)	2,012,102
	Total Westlake Chemical Corporation stockholders' equity	2,911,511			4,097,276			835,839			628,588			(5,561,703		)	2,911,511
	Noncontrolling interests	—			—			—			290,377			—			290,377
	Total equity	2,911,511			4,097,276			835,839			918,965			(5,561,703		)	3,201,888
	Total liabilities and equity	$	4,728,900		$	5,013,978		$	1,094,230		$	1,265,969		$	(6,889,087	)	$	5,213,990
Condensed Consolidating Financial Information Statement Of Operations	Condensed Consolidating Financial Information for the Three Months Ended March 31, 2015
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Statement of Operations
	Net sales	$	—		$	903,492		$	258,391		$	245,643		$	(303,995	)	$	1,103,531
	Cost of sales	—			727,399			162,164			228,269			(298,847		)	818,985
	Gross profit	—			176,093			96,227			17,374			(5,148		)	284,546
	Selling, general and administrative expenses	413			43,684			5,046			11,271			(5,148		)	55,266
	(Loss) income from operations	(413		)	132,409			91,181			6,103			—			229,280
	Interest expense	(10,752		)	(1		)	(1,376		)	(42		)	2,580			(9,591		)
	Other income, net	6,612			2,827			5			2,232			(2,580		)	9,096
	(Loss) income before income taxes	(4,553		)	135,235			89,810			8,293			—			228,785
	(Benefit from) provision for income taxes	(1,578		)	77,999			467			1,490			—			78,378
	Equity in net income of subsidiaries	149,317			79,891			—			9,452			(238,660		)	—
	Net income	146,342			137,127			89,343			16,255			(238,660		)	150,407
	Net income attributable to noncontrolling interests	—			—			—			4,065			—			4,065
	Net income attributable to Westlake Chemical Corporation	$	146,342		$	137,127		$	89,343		$	12,190		$	(238,660	)	$	146,342
	Comprehensive income (loss) attributable to Westlake Chemical	$	88,113		$	137,365		$	89,343		$	(47,319	)	$	(179,389	)	$	88,113
	Corporation
	Condensed Consolidating Financial Information for the Three Months Ended March 31, 2014
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Statement of Operations
	Net sales	$	—		$	844,342		$	560,014		$	9,117		$	(385,797	)	$	1,027,676
	Cost of sales	—			790,577			327,700			8,186			(385,797		)	740,666
	Gross profit	—			53,765			232,314			931			—			287,010
	Selling, general and administrative expenses	546			29,285			7,778			1,346			—			38,955
	(Loss) income from operations	(546		)	24,480			224,536			(415		)	—			248,055
	Interest expense	(8,947		)	(210		)	(3,591		)	—			3,591			(9,157		)
	Other income (expense), net	5,006			456			1,252			(614		)	(3,591		)	2,509
	(Loss) income before income taxes	(4,487		)	24,726			222,197			(1,029		)	—			241,407
	(Benefit from) provision for income taxes	(1,558		)	6,787			78,323			(177		)	—			83,375
	Equity in net income of subsidiaries	160,961			143,874			—			—			(304,835		)	—
	Net income (loss) attributable to Westlake Chemical Corporation	$	158,032		$	161,813		$	143,874		$	(852	)	$	(304,835	)	$	158,032
	Comprehensive income (loss) attributable to Westlake Chemical	$	158,866		$	161,948		$	143,874		$	(1,750	)	$	(304,072	)	$	158,866
	Corporation
Condensed Consolidating Financial Information Statement Of Cash Flows	Condensed Consolidating Financial Information for the Three Months Ended March 31, 2015
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Statement of Cash Flows
	Cash flows from operating activities
	Net income	$	146,342		$	137,127		$	89,343		$	16,255		$	(238,660	)	$	150,407
	Adjustments to reconcile net income to net cash (used for)
	provided by operating activities
	Depreciation and amortization	501			29,592			19,803			9,246			—			59,142
	Deferred income taxes	(124		)	6,431			54			(1,030		)	—			5,331
	Net changes in working capital and other	(151,572		)	(114,779		)	6,973			(3,606		)	238,660			(24,324		)
	Net cash (used for) provided by operating activities	(4,853		)	58,371			116,173			20,865			—			190,556
	Cash flows from investing activities
	Additions to property, plant and equipment	—			(47,385		)	(39,540		)	(8,897		)	—			(95,822		)
	Settlements of derivative instruments	—			(833		)	—			—			—			(833		)
	Net cash used for investing activities	—			(48,218		)	(39,540		)	(8,897		)	—			(96,655		)
	Cash flows from financing activities
	Intercompany financing	72,634			(99,765		)	30,191			(3,060		)	—			—
	Dividends paid	(21,964		)	—			—			—			—			(21,964		)
	Distributions paid	—			89,161			(95,364		)	2,645			—			(3,558		)
	Proceeds from exercise of stock options	157			—			—			—			—			157
	Repurchase of common stock for treasury	(2,000		)	—			—			—			—			(2,000		)
	Windfall tax benefits from share-based payment arrangements	1,701			—			—			—			—			1,701
	Net cash provided by (used for) financing activities	50,528			(10,604		)	(65,173		)	(415		)	—			(25,664		)
	Effect of exchange rate changes on cash and cash equivalents	—			—			—			(3,189		)	—			(3,189		)
	Net increase (decrease) in cash and cash equivalents	45,675			(451		)	11,460			8,364			—			65,048
	Cash and cash equivalents at beginning of period	655,947			3,057			131,545			90,052			—			880,601
	Cash and cash equivalents at end of period	$	701,622		$	2,606		$	143,005		$	98,416		$	—		$	945,649
	Condensed Consolidating Financial Information for the Three Months Ended March 31, 2014
		Westlake			100% Owned			OpCo			Non-			Eliminations			Consolidated
		Chemical			Guarantor			(Less Than			Guarantor
		Corporation			Subsidiaries			100% Owned			Subsidiaries
								Guarantor
								Subsidiary)
	Statement of Cash Flows
	Cash flows from operating activities
	Net income (loss)	$	158,032		$	161,813		$	143,874		$	(852	)	$	(304,835	)	$	158,032
	Adjustments to reconcile net income (loss) to net cash (used for)
	provided by operating activities
	Depreciation and amortization	365			26,394			19,014			564			—			46,337
	Deferred income taxes	(162		)	5,220			3,267			(50		)	—			8,275
	Net changes in working capital and other	(165,553		)	(169,342		)	31,731			(1,810		)	304,835			(139		)
	Net cash (used for) provided by operating activities	(7,318		)	24,085			197,886			(2,148		)	—			212,505
	Cash flows from investing activities
	Additions to property, plant and equipment	—			(59,254		)	(51,305		)	(182		)	—			(110,741		)
	Proceeds from disposition of assets	—			12			—			—			—			12
	Proceeds from sales and maturities of securities	30,119			—			—			—			—			30,119
	Purchase of securities	(49,025		)	—			—			—			—			(49,025		)
	Settlements of derivative instruments	—			—			(409		)	—			—			(409		)
	Net cash used for investing activities	(18,906		)	(59,242		)	(51,714		)	(182		)	—			(130,044		)
	Cash flows from financing activities
	Intercompany financing	106,903			(155,387		)	46,041			2,443			—			—
	Net distributions prior to Westlake Partners initial public offering	—			192,213			(192,213		)	—			—			—
	Dividends paid	(16,789		)	—			—			—			—			(16,789		)
	Proceeds from exercise of stock options	2,158			—			—			—			—			2,158
	Windfall tax benefits from share-based payment arrangements	3,512			—			—			—			—			3,512
	Net cash provided by (used for) financing activities	95,784			36,826			(146,172		)	2,443			—			(11,119		)
	Net increase in cash and cash equivalents	69,560			1,669			—			113			—			71,342
	Cash and cash equivalents at beginning of period	420,948			6,227			—			34,126			—			461,301
	Cash and cash equivalents at end of period	$	490,508		$	7,896		$	—		$	34,239		$	—		$	532,643

Financial_Instruments_Cash_Equ

Financial Instruments Cash Equivalents (Details) (Held-to-maturity Securities, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Held-to-maturity Securities
Cash Equivalents [Line Items]
Cash equivalents	$496,843	$509,811

Financial_Instruments_Marketab

Financial Instruments (Marketable Securities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]
Noncurrent	$17,033	$15,414
Total available-for-sale securities	$17,033	$15,414

Financial_Instruments_Availabl

Financial Instruments (Available-for-sale Securities) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cost	$15,043		$15,050
Gross Unrealized Gains	1,990		364
Gross Unrealized Losses	0		0
Fair Value	-17,033		-15,414
Net unrealized gains on available-for-sale securities	1,276		233
Income tax on gains from available-for-sale securities	714		131
Proceeds from sales and maturities of securities	0	30,119
Gross realized gains	0	13
Gross realized losses	0	-38
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost	15,043		15,050
Gross Unrealized Gains	1,990		364
Gross Unrealized Losses	0		0
Fair Value	($17,033)		($15,414)

Accounts_Receivable_Details

Accounts Receivable (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accounts Receivable, Net [Abstract]
Trade customers	$500,262	$525,546
Affiliates	449	437
Allowance for doubtful accounts	-13,259	-13,468
Receivables from trade customers and affiliates, net	487,452	512,515
Federal and state taxes	21,289	8,919
Other	18,386	39,232
Accounts receivable, net	$527,127	$560,666

Inventories_Details

Inventories (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]
Finished products	$278,501	$300,909
Inventory, Work in Process and Raw Materials, Net of Reserves	135,903	158,635
Materials and supplies	65,976	66,232
Inventories	$480,380	$525,776

Property_Plant_and_Equipment_D

Property, Plant and Equipment (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, plant and equipment	$2,751,486		$2,757,557
Depreciation expense on property, plant and equipment	$49,658	$38,061

Other_Assets_Additional_Inform

Other Assets (Additional Information) (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Other Assets [Line Items]
Amortization expense on intangible assets, included in other assets	$9,484	$8,276
Olefins
Other Assets [Line Items]
Goodwill	29,990		29,990
Vinyls
Other Assets [Line Items]
Goodwill	$32,026		$32,026

LongTerm_Debt_Schedule_of_Long

Long-Term Debt (Schedule of Long-term Debt) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term debt	$764,027	$763,997
3.60% Senior Notes Due 2022
Debt Instrument [Line Items]
Maturity	2022
Stated interest rate	3.60%
Senior notes	249,138	249,108
6 1/2% Senior Notes Due 2029
Debt Instrument [Line Items]
Maturity	2029
Stated interest rate	6.50%
Senior notes	100,000	100,000
6 3/4% Senior Notes Due 2032
Debt Instrument [Line Items]
Maturity	2032
Stated interest rate	6.75%
Senior notes	250,000	250,000
2035 GO Zone 6 1/2% Notes
Debt Instrument [Line Items]
Maturity	2035
Stated interest rate	6.50%
Senior notes	89,000	89,000
2035 IKE Zone 6 1/2% Notes
Debt Instrument [Line Items]
Maturity	2035
Stated interest rate	6.50%
Senior notes	65,000	65,000
Loan related to tax-exempt waste disposal revenue bonds due 2027
Debt Instrument [Line Items]
Maturity	2027
Non-current loan payable	$10,889	$10,889

LongTerm_Debt_Revolving_Credit

Long-Term Debt (Revolving Credit Facility) (Details) (Line of Credit, USD $)	3 Months Ended
	Mar. 31, 2015
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$400,000,000
Revolving credit facility, amount outstanding	0
Percentage of commitment on borrowing availability	0.25%
Letters of credit outstanding	29,959,000
Remaining borrowing capacity	370,041,000
LIBOR [Member]
Line of Credit Facility [Line Items]
Maximum basis spread, provided company is rated investment grade	1.50%
Minimum
Line of Credit Facility [Line Items]
Increase in credit facility borrowings	25,000,000
Minimum | LIBOR [Member]
Line of Credit Facility [Line Items]
Percentage added to basis to find interest rate	1.25%
Minimum | Base Rate [Member]
Line of Credit Facility [Line Items]
Percentage added to basis to find interest rate	0.00%
Maximum
Line of Credit Facility [Line Items]
Increase in credit facility borrowings	$200,000,000
Maximum | LIBOR [Member]
Line of Credit Facility [Line Items]
Percentage added to basis to find interest rate	1.75%
Maximum | Base Rate [Member]
Line of Credit Facility [Line Items]
Percentage added to basis to find interest rate	0.50%

Stockholders_Equity_Changes_in

Stockholders' Equity (Changes in Stockholders' Equity) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	$3,201,888	$2,418,603
Net income	150,407	158,032
Pension and other post- retirement benefits liability	427	135
Foreign currency translation adjustments	-59,698	-898
Net unrealized holding gains on investments	1,042	1,597
Common stock repurchased	-2,000
Shares issuedbstock- based compensation	157	2,158
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,041	5,734
Dividends paid	-21,964	-16,789
Distributions to noncontrolling interests	-3,558
Amount, ending balance	3,270,742	2,568,572
Common Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	1,347	1,346
Shares issuedbstock- based compensation	0	1
Amount, ending balance	1,347	1,347
Treasury Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	-96,372		-46,220
Common stock repurchased	-2,000
Shares issuedbstock- based compensation	97
Amount, ending balance	-98,275	-46,220	-46,220
Additional Paid-in Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	530,441	511,432
Shares issuedbstock- based compensation	60	2,157
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,041	5,734
Amount, ending balance	534,542	519,323
Retained Earnings [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	2,555,528	1,954,661
Net income	146,342	158,032
Dividends paid	-21,964	-16,789
Amount, ending balance	2,679,906	2,095,904
AOCI Attributable to Parent [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	-79,433	-2,616
Pension and other post- retirement benefits liability	427	135
Foreign currency translation adjustments	-59,698	-898
Net unrealized holding gains on investments	1,042	1,597
Amount, ending balance	-137,662	-1,782
Noncontrolling Interest [Member]
Schedule of Capitalization, Equity [Line Items]
Amount, beginning balance	290,377
Net income	4,065
Distributions to noncontrolling interests	-3,558
Amount, ending balance	$290,884

Stockholders_Equity_Changes_in1

Stockholders' Equity (Changes in AOCI) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	($79,433)	($2,616)
Other comprehensive loss before reclassifications	-58,656	683
Amounts reclassified from accumulated other comprehensive loss	427	151
Other comprehensive (loss) income	-58,229	834
Accumulated other comprehensive income (loss), ending balance	-137,662	-1,782
Benefits Liability, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	-23,442	-6,696
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	427	135
Other comprehensive (loss) income	427	135
Accumulated other comprehensive income (loss), ending balance	-23,015	-6,561
Cumulative Foreign Currency Exchange
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	-56,224	3,904
Other comprehensive loss before reclassifications	-59,698	-898
Amounts reclassified from accumulated other comprehensive loss	0	0
Other comprehensive (loss) income	-59,698	-898
Accumulated other comprehensive income (loss), ending balance	-115,922	3,006
Net Unrealized Holding Gains on Investmetnts, Net of Tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), beginning balance	233	176
Other comprehensive loss before reclassifications	1,042	1,581
Amounts reclassified from accumulated other comprehensive loss	0	16
Other comprehensive (loss) income	1,042	1,597
Accumulated other comprehensive income (loss), ending balance	$1,275	$1,773

Stockholders_Equity_Reclassifi

Stockholders' Equity (Reclassifications in AOCI) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gain on available-for-sale investments	$9,096		$2,509
Provision for income taxes	-78,378		-83,375
Net income attributable to Westlake Chemical Corporation	146,342		158,032
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income attributable to Westlake Chemical Corporation	-427		-151
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service costs	0	[1]	-87	[1]
Net loss	-652	[1]	-132	[1]
Income before income taxes	-652		-219
Provision for income taxes	225		84
Net income attributable to Westlake Chemical Corporation	-427		-135
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized gain on available-for-sale investments	0		-25
Provision for income taxes	0		9
Net income attributable to Westlake Chemical Corporation	$0		($16)
[1]	These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 10 (Employee Benefits) to the financial statements included in the 2014 Form 10-K.

Pension_and_PostRetirement_Ben2

Pension and Post-Retirement Benefit Costs (Components of Net Periodic Benefit Cost) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
United States Pension Plan of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$28	$84
Interest cost	544	595
Expected return on plan assets	-819	-809
Amortization of prior service cost	0	74
Amortization of net loss	290	63
Net periodic benefit cost	-43	-7
Foreign Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	422
Interest cost	535
Expected return on plan assets	0
Amortization of prior service cost	0
Amortization of net loss	266
Net periodic benefit cost	-1,223
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5
Interest cost	149	181
Amortization of prior service cost	0	13
Amortization of net loss	96	69
Net periodic benefit cost	($251)	($268)

Pension_and_PostRetirement_Ben3

Pension and Post-Retirement Benefit Costs (Additional Information) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Salaried Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	$0	$388
Estimated future employer contributions for next fiscal year	0
Wage Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	112	290
Estimated future employer contributions for next fiscal year	$237

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation expense	$2,340	$2,222

Derivative_Instruments_Textual

Derivative Instruments (Textual) (Detail) (Commodity Forward Contracts [Member], Designated As Fair Value Hedges)	Mar. 31, 2015	Mar. 31, 2014
	instrument	instrument
Commodity Forward Contracts [Member] | Designated As Fair Value Hedges
Derivative [Line Items]
Number of derivative instruments	0	0

Derivative_Instruments_Fair_Va

Derivative Instruments (Fair Values of Derivative Instruments in Consolidated Balance Sheets) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Accrued Liabilities
Derivatives, Fair Value [Line Items]
Total derivative liabilities	$6,861	$10,108
Accounts Receivable
Derivatives, Fair Value [Line Items]
Total derivative assets	4,484	3,145
Forward Contracts [Member] | Accrued Liabilities
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	5,060	6,549
Forward Contracts [Member] | Accounts Receivable
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	2,927	3,145
Forward Contracts [Member] | Deferred charges and other assets, net
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Assets	1,557	0
Commodity Forward Contracts [Member] | Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Not designated as hedging instruments, Derivative Liabilities	$1,801	$3,559

Derivative_Instruments_Impact_

Derivative Instruments (Impact of Derivative Instruments on Income) (Details) (Derivatives Not Designated As Hedging Instruments, Forward Contracts [Member], Cost of Sales, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivatives Not Designated As Hedging Instruments | Forward Contracts [Member] | Cost of Sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$4,241	($611)

Fair_Value_Measurements_Summar

Fair Value Measurements (Summary of Assets and Liabilities Accounted at Fair Value on Recurring Basis) (Details) (Recurring, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$17,033	$15,414
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	17,033	15,414
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	0	0
Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	4,484	3,145
Risk management liabilities - Commodity forward contracts	-6,861	-10,108
Forward Contracts [Member] | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	4,209	3,143
Risk management liabilities - Commodity forward contracts	-17	0
Forward Contracts [Member] | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	275	2
Risk management liabilities - Commodity forward contracts	($6,844)	($10,108)

Fair_Value_Measurements_Summar1

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
3.60% Senior Notes Due 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2022
Stated interest rate	3.60%
3.60% Senior Notes Due 2022 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	249,138	$249,108
3.60% Senior Notes Due 2022 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	253,240	248,630
6 1/2% Senior Notes Due 2029
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2029
Stated interest rate	6.50%
6 1/2% Senior Notes Due 2029 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	100,000	100,000
6 1/2% Senior Notes Due 2029 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	118,493	116,384
6 3/4% Senior Notes Due 2032
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2032
Stated interest rate	6.75%
6 3/4% Senior Notes Due 2032 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	250,000	250,000
6 3/4% Senior Notes Due 2032 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	280,285	285,545
2035 GO Zone 6 1/2% Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2035
Stated interest rate	6.50%
2035 GO Zone 6 1/2% Notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	89,000	89,000
2035 GO Zone 6 1/2% Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	105,298	106,504
2035 IKE Zone 6 1/2% Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2035
Stated interest rate	6.50%
2035 IKE Zone 6 1/2% Notes | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	65,000	65,000
2035 IKE Zone 6 1/2% Notes | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	76,903	77,784
Loan related to tax-exempt waste disposal revenue bonds due 2027
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity	2027
Loan related to tax-exempt waste disposal revenue bonds due 2027 | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	10,889	10,889
Loan related to tax-exempt waste disposal revenue bonds due 2027 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loans	10,889	$10,889

Income_Taxes_Detail

Income Taxes (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	34.30%	34.50%
U.S. federal statutory income tax rate	35.00%	35.00%
Anticipated reductions to unrecognized tax benefits within next twelve months	$0
Income Tax Examination, Penalties and Interest Accrued	$0

Earnings_per_Share_Additional_

Earnings per Share (Additional Information) (Detail)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Number of options excluded from computation of diluted earnings per share	241,312	69,662

Earnings_per_Share_Schedule_of

Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$146,342	$158,032
Less: Net income attributable to participating securities	-200	-384
Net income attributable to common shareholders	$146,142	$157,648

Earnings_per_Share_Reconciliat

Earnings per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Weighted average common sharesbbasic	132,714,566	133,072,254
Plus incremental shares from: Assumed exercise of options	490,740	540,670
Weighted average common shares-diluted	133,205,306	133,612,924
Earnings per share: Basic	$1.10	$1.18
Earnings per share: Diluted	$1.10	$1.18

Supplemental_Information_Detai

Supplemental Information (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other liabilities	$157,130	$174,859
Non-current pension obligation, a component of other liabilities	$123,207	$136,296

Commitments_and_Contingencies_

Commitments and Contingencies (Additional Information) (Detail) (USD $)	12 Months Ended	92 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Mar. 31, 2015
Unfavorable Regulatory Action [Member]
Commitments and Contingencies Disclosure [Line Items]
Possible amount of claims in settlement for compliance violations		200
Goodrich And PolyOne [Member]
Commitments and Contingencies Disclosure [Line Items]
Costs incurred for environmental remediation services	2,805
Goodrich And PolyOne [Member] | Settled Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Percentage of costs related to environmental issues to be paid by PolyOne		100.00%
Minimum number of years between arbitrations		5 years
Goodrich And PolyOne [Member] | Pending Litigation [Member]
Commitments and Contingencies Disclosure [Line Items]
Reimbursement of remediation costs sought by PolyOne		1,400

Segment_Information_Additional

Segment Information (Additional Information) (Detail)	3 Months Ended
	Mar. 31, 2015
	Segment
Segment Reporting [Abstract]
Number of segments	2

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Net external sales	$1,103,531	$1,027,676
Income (loss) from operations	229,280	248,055
Depreciation and amortization	58,641	45,972
Other income, net	9,096	2,509
Provision for (benefit from) income taxes	78,378	83,375
Capital expenditures	95,822	110,741
Olefins
Segment Reporting Information [Line Items]
Net external sales	583,077	722,798
Income (loss) from operations	191,103	272,333
Depreciation and amortization	26,939	26,647
Other income, net	2,552	1,454
Provision for (benefit from) income taxes	66,457	93,550
Capital expenditures	55,300	29,074
Vinyls
Segment Reporting Information [Line Items]
Net external sales	520,454	304,878
Income (loss) from operations	47,086	-21,114
Depreciation and amortization	31,584	19,168
Other income, net	5,503	-34
Provision for (benefit from) income taxes	12,805	-10,070
Capital expenditures	36,855	81,120
Corporate and Other
Segment Reporting Information [Line Items]
Income (loss) from operations	-8,909	-3,164
Depreciation and amortization	118	157
Other income, net	1,041	1,089
Provision for (benefit from) income taxes	-884	-105
Capital expenditures	3,667	547
Polyethylene | Olefins
Segment Reporting Information [Line Items]
Net external sales	409,432	487,144
Ethylene, Styrene And Other | Olefins
Segment Reporting Information [Line Items]
Net external sales	173,645	235,654
PVC, Caustic Soda And Other | Vinyls
Segment Reporting Information [Line Items]
Net external sales	416,988	190,527
Building Products | Vinyls
Segment Reporting Information [Line Items]
Net external sales	103,466	114,351
Intersegment sales
Segment Reporting Information [Line Items]
Net external sales	23,832	57,196
Intersegment sales | Olefins
Segment Reporting Information [Line Items]
Net external sales	23,462	56,853
Intersegment sales | Vinyls
Segment Reporting Information [Line Items]
Net external sales	$370	$343

Segment_Information_Reconcilia

Segment Information (Reconciliation of Total Segment Income from Operations to Consolidated Income before Income Taxes) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting [Abstract]
Income from operations	$229,280	$248,055
Interest expense	-9,591	-9,157
Other income, net	9,096	2,509
Income before income taxes	$228,785	$241,407

Segment_Information_Total_Asse

Segment Information (Total Assets) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$5,179,785	$5,213,990
Olefins
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,783,845	1,785,895
Vinyls
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,510,470	2,618,646
Corporate and Other
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$885,470	$809,449

Subsequent_Events_Subsequent_E

Subsequent Events Subsequent Events (Details) (Subsequent Event [Member], Limited Partner [Member], USD $)	0 Months Ended
	Apr. 29, 2015
Westlake Chemical OpCo LP [Member]
Subsequent Event [Line Items]
Partnership's ownership interest	86.70%
Westlake Chemical Partners LP [Member] | Subsidiary of Common Parent [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity	300,000,000
Westlake Chemical Partners LP [Member] | Westlake Chemical OpCo LP [Member]
Subsequent Event [Line Items]
Additional limited partner interest purchased	2.70%
Amount paid to purchase additional limited partner interest	135,341,000
Partnership's ownership interest	13.30%

Guarantor_Disclosures_Addition

Guarantor Disclosures (Additional Information) (Detail) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Less than percentage owned in subsidiary	100.00%
3.60% Senior Notes Due 2022
Condensed Financial Statements, Captions [Line Items]
Stated interest rate	3.60%
Maturity	2022
Minimum debt amount guaranteed by subsidiaries	5,000

Guarantor_Disclosures_Condense

Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$945,649	$880,601	$532,643	$461,301
Accounts receivable, net	527,127	560,666
Inventories	480,380	525,776
Prepaid expenses and other current assets	18,018	11,807
Deferred income taxes	30,988	32,437
Total current assets	2,002,162	2,011,287
Property, plant and equipment, net	2,751,486	2,757,557
Equity investments	64,721	61,305
Other assets, net	361,416	383,841
Total assets	5,179,785	5,213,990
Accounts payable	247,493	261,062
Accrued liabilities	205,714	276,118
Total current liabilities	453,207	537,180
Long-term debt	764,027	763,997
Deferred income taxes	534,679	536,066
Other liabilities	157,130	174,859
Total liabilities	1,909,043	2,012,102
Total Westlake Chemical Corporation stockholders' equity	2,979,858	2,911,511
Noncontrolling interests	290,884	290,377
Total equity	3,270,742	3,201,888	2,568,572	2,418,603
Total liabilities and equity	5,179,785	5,213,990
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	701,622	655,947	490,508	420,948
Accounts receivable, net	11,605	8,451
Inventories	0	0
Prepaid expenses and other current assets	92	172
Deferred income taxes	409	409
Total current assets	713,728	664,979
Property, plant and equipment, net	0	0
Equity investments	4,123,427	4,033,378
Other assets, net	31,209	30,543
Total assets	4,868,364	4,728,900
Accounts payable	1,118,864	1,055,527
Accrued liabilities	16,504	8,754
Total current liabilities	1,135,368	1,064,281
Long-term debt	753,138	753,108
Deferred income taxes	0	0
Other liabilities	0	0
Total liabilities	1,888,506	1,817,389
Total Westlake Chemical Corporation stockholders' equity	2,979,858	2,911,511
Noncontrolling interests	0	0
Total equity	2,979,858	2,911,511
Total liabilities and equity	4,868,364	4,728,900
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	2,606	3,057	7,896	6,227
Accounts receivable, net	1,497,572	1,454,709
Inventories	395,664	414,975
Prepaid expenses and other current assets	18,236	9,485
Deferred income taxes	29,832	29,832
Total current assets	1,943,910	1,912,058
Property, plant and equipment, net	1,500,234	1,477,515
Equity investments	1,232,093	1,237,080
Other assets, net	415,180	387,325
Total assets	5,091,417	5,013,978
Accounts payable	153,645	160,834
Accrued liabilities	150,074	203,608
Total current liabilities	303,719	364,442
Long-term debt	10,889	10,889
Deferred income taxes	503,540	497,919
Other liabilities	38,625	43,452
Total liabilities	856,773	916,702
Total Westlake Chemical Corporation stockholders' equity	4,234,644	4,097,276
Noncontrolling interests	0	0
Total equity	4,234,644	4,097,276
Total liabilities and equity	5,091,417	5,013,978
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	143,005	131,545	0	0
Accounts receivable, net	54,979	56,049
Inventories	4,564	6,634
Prepaid expenses and other current assets	122	212
Deferred income taxes	0	0
Total current assets	202,670	194,440
Property, plant and equipment, net	866,546	842,057
Equity investments	0	0
Other assets, net	53,832	57,733
Total assets	1,123,048	1,094,230
Accounts payable	27,395	17,680
Accrued liabilities	6,104	11,225
Total current liabilities	33,499	28,905
Long-term debt	257,829	227,638
Deferred income taxes	1,902	1,848
Other liabilities	0	0
Total liabilities	293,230	258,391
Total Westlake Chemical Corporation stockholders' equity	829,818	835,839
Noncontrolling interests	0	0
Total equity	829,818	835,839
Total liabilities and equity	1,123,048	1,094,230
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	98,416	90,052	34,239	34,126
Accounts receivable, net	128,116	135,133
Inventories	80,152	104,167
Prepaid expenses and other current assets	2,160	1,938
Deferred income taxes	747	2,196
Total current assets	309,591	333,486
Property, plant and equipment, net	384,706	437,985
Equity investments	351,048	352,550
Other assets, net	124,633	141,948
Total assets	1,169,978	1,265,969
Accounts payable	89,383	95,856
Accrued liabilities	58,975	77,372
Total current liabilities	148,358	173,228
Long-term debt	0	0
Deferred income taxes	34,846	42,369
Other liabilities	118,505	131,407
Total liabilities	301,709	347,004
Total Westlake Chemical Corporation stockholders' equity	577,385	628,588
Noncontrolling interests	290,884	290,377
Total equity	868,269	918,965
Total liabilities and equity	1,169,978	1,265,969
Eliminations
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	-1,165,145	-1,093,676
Inventories	0	0
Prepaid expenses and other current assets	-2,592	0
Deferred income taxes	0	0
Total current assets	-1,167,737	-1,093,676
Property, plant and equipment, net	0	0
Equity investments	-5,641,847	-5,561,703
Other assets, net	-263,438	-233,708
Total assets	-7,073,022	-6,889,087
Accounts payable	-1,141,794	-1,068,835
Accrued liabilities	-25,943	-24,841
Total current liabilities	-1,167,737	-1,093,676
Long-term debt	-257,829	-227,638
Deferred income taxes	-5,609	-6,070
Other liabilities	0	0
Total liabilities	-1,431,175	-1,327,384
Total Westlake Chemical Corporation stockholders' equity	-5,641,847	-5,561,703
Noncontrolling interests	0	0
Total equity	-5,641,847	-5,561,703
Total liabilities and equity	($7,073,022)	($6,889,087)

Guarantor_Disclosures_Condense1

Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net sales	$1,103,531	$1,027,676
Cost of sales	818,985	740,666
Gross profit	284,546	287,010
Selling, general and administrative expenses	55,266	38,955
Income from operations	229,280	248,055
Interest expense	-9,591	-9,157
Other income, net	9,096	2,509
Income before income taxes	228,785	241,407
Provision for (benefit from) income taxes	78,378	83,375
Equity in net income of subsidiaries	0	0
Net income	150,407	158,032
Net income attributable to noncontrolling interests	4,065	0
Net income attributable to Westlake Chemical Corporation	146,342	158,032
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,113	158,866
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general and administrative expenses	413	546
Income from operations	-413	-546
Interest expense	-10,752	-8,947
Other income, net	6,612	5,006
Income before income taxes	-4,553	-4,487
Provision for (benefit from) income taxes	-1,578	-1,558
Equity in net income of subsidiaries	149,317	160,961
Net income	146,342	158,032
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	146,342	158,032
Comprehensive income (loss) attributable to Westlake Chemical Corporation	88,113	158,866
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	903,492	844,342
Cost of sales	727,399	790,577
Gross profit	176,093	53,765
Selling, general and administrative expenses	43,684	29,285
Income from operations	132,409	24,480
Interest expense	-1	-210
Other income, net	2,827	456
Income before income taxes	135,235	24,726
Provision for (benefit from) income taxes	77,999	6,787
Equity in net income of subsidiaries	79,891	143,874
Net income	137,127	161,813
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	137,127	161,813
Comprehensive income (loss) attributable to Westlake Chemical Corporation	137,365	161,948
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net sales	258,391	560,014
Cost of sales	162,164	327,700
Gross profit	96,227	232,314
Selling, general and administrative expenses	5,046	7,778
Income from operations	91,181	224,536
Interest expense	-1,376	-3,591
Other income, net	5	1,252
Income before income taxes	89,810	222,197
Provision for (benefit from) income taxes	467	78,323
Equity in net income of subsidiaries	0	0
Net income	89,343	143,874
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	89,343	143,874
Comprehensive income (loss) attributable to Westlake Chemical Corporation	89,343	143,874
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net sales	245,643	9,117
Cost of sales	228,269	8,186
Gross profit	17,374	931
Selling, general and administrative expenses	11,271	1,346
Income from operations	6,103	-415
Interest expense	-42	0
Other income, net	2,232	-614
Income before income taxes	8,293	-1,029
Provision for (benefit from) income taxes	1,490	-177
Equity in net income of subsidiaries	9,452	0
Net income	16,255	-852
Net income attributable to noncontrolling interests	4,065
Net income attributable to Westlake Chemical Corporation	12,190	-852
Comprehensive income (loss) attributable to Westlake Chemical Corporation	-47,319	-1,750
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net sales	-303,995	-385,797
Cost of sales	-298,847	-385,797
Gross profit	-5,148	0
Selling, general and administrative expenses	-5,148	0
Income from operations	0	0
Interest expense	2,580	3,591
Other income, net	-2,580	-3,591
Income before income taxes	0	0
Provision for (benefit from) income taxes	0	0
Equity in net income of subsidiaries	-238,660	-304,835
Net income	-238,660	-304,835
Net income attributable to noncontrolling interests	0
Net income attributable to Westlake Chemical Corporation	-238,660	-304,835
Comprehensive income (loss) attributable to Westlake Chemical Corporation	($179,389)	($304,072)

Guarantor_Disclosures_Condense2

Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income	$150,407	$158,032
Depreciation and amortization	59,142	46,337
Deferred income taxes	5,331	8,275
Net changes in working capital and other	-24,324	-139
Net cash provided by operating activities	190,556	212,505
Additions to property, plant and equipment	-95,822	-110,741
Proceeds from disposition of assets	0	12
Proceeds from sales and maturities of securities	0	30,119
Purchase of securities	0	-49,025
Settlements of derivative instruments	-833	-409
Net cash used for investing activities	-96,655	-130,044
Intercompany financing	0	0
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	-3,558
Dividends paid	-21,964	-16,789
Proceeds from exercise of stock options	157	2,158
Repurchase of common stock for treasury	-2,000
Windfall tax benefits from share-based payment arrangements	1,701	3,512
Net cash provided by financing activities	-25,664	-11,119
Effect of exchange rate changes on cash and cash equivalents	-3,189	0
Net increase in cash and cash equivalents	65,048	71,342
Cash and cash equivalents at beginning of period	880,601	461,301
Cash and cash equivalents at end of period	945,649	532,643
Westlake Chemical Corporation
Condensed Financial Statements, Captions [Line Items]
Net income	146,342	158,032
Depreciation and amortization	501	365
Deferred income taxes	-124	-162
Net changes in working capital and other	-151,572	-165,553
Net cash provided by operating activities	-4,853	-7,318
Additions to property, plant and equipment	0	0
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		30,119
Purchase of securities		-49,025
Settlements of derivative instruments	0	0
Net cash used for investing activities	0	-18,906
Intercompany financing	72,634	106,903
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	0
Dividends paid	-21,964	-16,789
Proceeds from exercise of stock options	157	2,158
Repurchase of common stock for treasury	-2,000
Windfall tax benefits from share-based payment arrangements	1,701	3,512
Net cash provided by financing activities	50,528	95,784
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	45,675	69,560
Cash and cash equivalents at beginning of period	655,947	420,948
Cash and cash equivalents at end of period	701,622	490,508
100% Owned Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	137,127	161,813
Depreciation and amortization	29,592	26,394
Deferred income taxes	6,431	5,220
Net changes in working capital and other	-114,779	-169,342
Net cash provided by operating activities	58,371	24,085
Additions to property, plant and equipment	-47,385	-59,254
Proceeds from disposition of assets		12
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	-833	0
Net cash used for investing activities	-48,218	-59,242
Intercompany financing	-99,765	-155,387
Net distributions prior to WLKP initial public offering		192,213
Distribution Made to Limited Partner, Cash Distributions Paid	89,161
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	-10,604	36,826
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	-451	1,669
Cash and cash equivalents at beginning of period	3,057	6,227
Cash and cash equivalents at end of period	2,606	7,896
OpCo (Less Than 100% Owned Guarantor Subsidiary)
Condensed Financial Statements, Captions [Line Items]
Net income	89,343	143,874
Depreciation and amortization	19,803	19,014
Deferred income taxes	54	3,267
Net changes in working capital and other	6,973	31,731
Net cash provided by operating activities	116,173	197,886
Additions to property, plant and equipment	-39,540	-51,305
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	-409
Net cash used for investing activities	-39,540	-51,714
Intercompany financing	30,191	46,041
Net distributions prior to WLKP initial public offering		-192,213
Distribution Made to Limited Partner, Cash Distributions Paid	-95,364
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	-65,173	-146,172
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	11,460	0
Cash and cash equivalents at beginning of period	131,545	0
Cash and cash equivalents at end of period	143,005	0
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Net income	16,255	-852
Depreciation and amortization	9,246	564
Deferred income taxes	-1,030	-50
Net changes in working capital and other	-3,606	-1,810
Net cash provided by operating activities	20,865	-2,148
Additions to property, plant and equipment	-8,897	-182
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	0
Net cash used for investing activities	-8,897	-182
Intercompany financing	-3,060	2,443
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	2,645
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	-415	2,443
Effect of exchange rate changes on cash and cash equivalents	-3,189
Net increase in cash and cash equivalents	8,364	113
Cash and cash equivalents at beginning of period	90,052	34,126
Cash and cash equivalents at end of period	98,416	34,239
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income	-238,660	-304,835
Depreciation and amortization	0	0
Deferred income taxes	0	0
Net changes in working capital and other	238,660	304,835
Net cash provided by operating activities	0	0
Additions to property, plant and equipment	0	0
Proceeds from disposition of assets		0
Proceeds from sales and maturities of securities		0
Purchase of securities		0
Settlements of derivative instruments	0	0
Net cash used for investing activities	0	0
Intercompany financing	0	0
Net distributions prior to WLKP initial public offering		0
Distribution Made to Limited Partner, Cash Distributions Paid	0
Dividends paid	0	0
Proceeds from exercise of stock options	0	0
Repurchase of common stock for treasury	0
Windfall tax benefits from share-based payment arrangements	0	0
Net cash provided by financing activities	0	0
Effect of exchange rate changes on cash and cash equivalents	0
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$0	$0