Westlake (WLK) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	WLK
Entity Registrant Name	WESTLAKE CHEMICAL CORP
Entity Central Index Key	1,262,823
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		129,107,447

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 678,233	$ 459,453
Accounts receivable, net	1,142,979	938,743
Inventories	834,835	801,100
Prepaid expenses and other current assets	34,860	48,493
Restricted cash	8,626	160,527
Total current assets	2,699,533	2,408,316
Property, plant and equipment, net	6,343,637	6,420,062
Other assets, net
Goodwill	1,011,342	946,553
Customer relationships, net	635,884	611,615
Other intangible assets, net	166,166	175,839
Deferred charges and other assets, net	387,563	327,868
Total other assets, net	2,200,955	2,061,875
Total assets	11,244,125	10,890,253
Current liabilities
Accounts payable	560,804	496,259
Accrued liabilities	609,472	537,483
Term loan	0	149,341
Total current liabilities	1,170,276	1,183,083
Long-term debt, net	3,349,402	3,678,654
Deferred income taxes	1,660,914	1,650,575
Pension and other post-retirement benefits	367,705	364,819
Other liabilities	144,329	121,077
Total liabilities	6,692,626	6,998,208
Stockholders' equity
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.01 par value, 300,000,000 shares authorized; 134,651,380 and 134,651,380 shares issued at September 30, 2017 and December 31, 2016, respectively	1,347	1,347
Common stock, held in treasury, at cost; 5,551,693 and 5,726,377 shares at September 30, 2017 and December 31, 2016, respectively	(314,694)	(319,339)
Additional paid-in capital	558,423	550,641
Retained earnings	3,837,644	3,412,286
Accumulated other comprehensive loss	(13,946)	(121,306)
Total Westlake Chemical Corporation stockholders' equity	4,068,774	3,523,629
Noncontrolling interests	482,725	368,416
Total equity	4,551,499	3,892,045
Total liabilities and equity	$ 11,244,125	$ 10,890,253

Consolidated Balance Sheets (U3

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value, in dollars per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, in dollars per share	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	134,651,380	134,651,380
Common stock, shares held in treasury	5,551,693	5,726,377

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 2,108,889	$ 1,279,028	$ 6,030,666	$ 3,340,276
Cost of sales	1,610,837	1,076,895	4,759,637	2,641,192
Gross profit	498,052	202,133	1,271,029	699,084
Selling, general and administrative expenses	125,642	72,729	379,919	179,757
Transaction and integration-related costs	6,663	82,841	22,949	90,550
Income (loss) from operations	365,747	46,563	868,161	428,777
Other income (expense)
Interest expense	(40,036)	(24,366)	(118,784)	(36,966)
Nonoperating Income (Expense)	2,058	41,265	6,591	52,091
Income before income taxes	327,769	63,462	755,968	443,902
Provision for (benefit from) income taxes	108,619	(6,552)	232,690	129,332
Net income	219,150	70,014	523,278	314,570
Net income attributable to noncontrolling interests	8,318	4,352	21,429	14,656
Net income attributable to Westlake Chemical Corporation	$ 210,832	$ 65,662	$ 501,849	$ 299,914
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (usd per share)	$ 1.62	$ 0.51	$ 3.87	$ 2.31
Diluted (usd per share)	$ 1.61	$ 0.51	$ 3.85	$ 2.29
Weighted average common shares outstanding:
Basic (in shares)	129,069,186	128,793,661	129,033,597	129,519,577
Diluted (in shares)	129,888,968	129,379,956	129,789,965	130,103,897
Dividends per common share (usd per share)	$ 0.2100	$ 0.1906	$ 0.5912	$ 0.5536

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 219,150	$ 70,014	$ 523,278	$ 314,570
Pension and other post-retirement benefits liability
Pension and other post-retirement reserves adjustment (excluding amortization)	0	(206)	0	(412)
Amortization of benefits liability	529	369	1,600	1,072
Income tax provision on pension and other post- retirement benefits liability	(193)	(60)	(543)	(251)
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	39,714	6,453	108,166	15,758
Income tax provision on foreign currency translation	(76)	0	(1,603)	0
Net unrealized holding gains (losses) on investments
Unrealized holding gains on investments	0	1,550	0	61,524
Reclassification of net realized gains to net income	0	(52,401)	0	(53,720)
Income tax provision on available-for-sale investments	0	18,270	0	(2,805)
Other	(96)	0	(260)	0
Other comprehensive income (loss), net of income taxes	39,878	(26,025)	107,360	21,166
Comprehensive income	259,028	43,989	630,638	335,736
Comprehensive income attributable to noncontrolling interests, net of tax of $846 and $0 for the three months ended September 30, 2017 and 2016, respectively; and $2,467 and $0 for the nine months ended September 30, 2017 and 2016, respectively.	4,628	4,352	17,288	14,656
Comprehensive income attributable to Westlake Chemical Corporation	$ 254,400	$ 39,637	$ 613,350	$ 321,080

Consolidated Statements of Com6

Consolidated Statements of Comprehensive Income (Unaudited) OCI Parenthetical - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
OCI Parenthetical [Abstract]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	$ 846	$ 0	$ 2,467	$ 0

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income	$ 523,278	$ 314,570
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	448,533	227,193
Provision for doubtful accounts	3,771	1,176
Amortization of debt issuance costs	3,471	1,018
Stock-based compensation expense	16,740	6,588
Loss from disposition of property, plant and equipment	14,319	6,541
Gains realized on previously held shares of Axiall common stock and from sales of securities	0	(53,720)
Write-off of debt issuance costs	659	0
Deferred income taxes	23,294	105,910
Windfall tax benefits from share-based payment arrangements	0	(1,190)
Dividends in excess of income from equity method investments	(2,132)	(61)
Gain on involuntary conversion of assets	(1,672)	0
Other losses (gains), net	(6,659)	833
Changes in operating assets and liabilities, net of effect of business acquisitions
Accounts receivable	(185,153)	(92,311)
Inventories	23,945	(6,124)
Prepaid expenses and other current assets	16,788	1,631
Accounts payable	60,899	34,109
Accrued liabilities	57,419	73,157
Other, net	(34,836)	(75,160)
Net cash provided by (used for) operating activities	962,664	544,160
Cash flows from investing activities
Acquisition of business, net of cash acquired	0	(2,437,829)
Additions to property, plant and equipment	(414,271)	(467,330)
Additions to cost method investment	(47,000)	(4,000)
Proceeds from disposition of assets	171	213
Proceeds from involuntary conversion of assets	1,672	0
Proceeds from sales and maturities of securities	0	662,938
Purchase of securities	0	(138,422)
Settlements of derivative instruments	(7)	(4,655)
Net cash used for investing activities	(459,435)	(2,389,085)
Cash flows from financing activities
Debt issuance costs	(376)	(35,207)
Dividends paid	(76,491)	(71,933)
Distributions to noncontrolling interests	(20,767)	(12,300)
Net proceeds from issuance of Westlake Chemical Partners LP common units	110,739	0
Proceeds from debt issuance	0	1,428,512
Proceeds from issuance of notes payable	5,946	5,597
Proceeds from term loan and drawdown of revolver	225,000	600,000
Restricted cash associated with term loan	154,000	(154,000)
Repayment of term loan	(150,000)	0
Repayment of notes payable	(6,695)	(10,602)
Repayment of revolver	(550,000)	(125,000)
Repurchase of common stock for treasury	0	(67,406)
Other	2,204	2,840
Net cash provided by (used for) financing activities	(306,440)	1,560,501
Effect of exchange rate changes on cash and cash equivalents	21,991	2,418
Net increase (decrease) in cash and cash equivalents	218,780	(282,006)
Cash and cash equivalents at beginning of period	459,453	662,525
Cash and cash equivalents at end of period	$ 678,233	$ 380,519

Basis of Financial Statements

Basis of Financial Statements	9 Months Ended
	Sep. 30, 2017
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, 2016 consolidated financial statements and notes thereto of Westlake Chemical Corporation (the "Company") included in the annual report on Form 10-K for the fiscal year ended December 31, 2016 (the " 2016 Form 10-K"), filed with the SEC on February 22, 2017 . These consolidated financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Company for the fiscal year ended December 31, 2016 . In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of September 30, 2017 , its results of operations for the three and nine months ended September 30, 2017 and 2016 and the changes in its cash position for the nine months ended September 30, 2017 and 2016 . 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, 2017 or any other interim period. The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Recent Accounting Pronouncements Revenue from Contracts with Customers (ASU No. 2014-09) 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. In 2016, the FASB issued various additional authoritative guidance for the new revenue recognition standard. The accounting standard will be effective for reporting periods beginning after December 15, 2017. The Company is in the process of evaluating the impact that the new accounting standard will have on its consolidated financial position, results of operations and cash flows. The Company has completed a preliminary assessment including detailed review of a representative sample of contracts with customers. The Company does not believe that adoption of the new accounting standard will materially impact timing or amounts of revenue recognized for the majority of its sales. The Company intends to elect the modified retrospective method of adoption. Recognition and Measurement of Financial Assets and Financial Liabilities (ASU No. 2016-01) In January 2016, the FASB issued an accounting standards update making certain changes principally to the current guidance for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. Among other things, the guidance (1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value, with changes in fair value recognized in net income; (2) provide entities with a policy election to record equity investments without readily determinable fair values at cost, less impairment, and subsequent adjustments for observable price changes (changes in the basis of these equity investments to be reported in net income); (3) requires an entity that has elected the fair value option for financial liabilities to recognize changes in fair value due to instrument-specific credit risk separately in other comprehensive income; (4) clarified current guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities; and (5) requires specific disclosure pertaining to financial assets and financial liabilities in the financial statements. The accounting standard will be effective for reporting periods beginning after December 15, 2017. 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. Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Company is in the process of evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-18) In November 2016, the FASB issued an accounting standards update to clarify certain existing principles in Accounting Standards Codification ("ASC") 230, Cash flows, including providing additional guidance related to transfers between cash and restricted cash and how entities present, in their statement of cash flows, the cash receipts and cash payments that directly affect the restricted cash accounts. The accounting standard will be effective for reporting periods beginning after December 15, 2017. Upon adoption of the accounting standards update, the Company will retrospectively adjust its financial statements to reflect restricted cash in the beginning and ending cash and restricted cash balances within the statements of cash flows. Transfers between cash and restricted cash will be excluded from net changes in cash and cash equivalents within the statements of cash flows. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in the ASC 606, Revenue from contracts with customers. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income — gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Retirement Benefits (ASU No. 2017-07) In March 2017, the FASB issued an accounting standards update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires employers to disaggregate the service cost component from the other components of net periodic benefit cost and report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The amendments also allow only the service cost component to be eligible for capitalization when applicable. The accounting standard will be effective for reporting periods beginning after December 15, 2017. 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. Compensation - Stock Compensation (ASU No. 2017-09) In May 2017, the FASB issued the accounting standards update to provide clarity and reduce both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require the application of modification accounting in Topic 718. Essentially, an entity will not have to account for the effects of a modification if: (1) the fair value of the modified award is the same immediately before and after the modification; (2) the vesting conditions of the modified award are the same immediately before and after the modification; and (3) the classification of the modified award as either an equity instrument or liability instrument is the same immediately before and after the modification. This update is to be applied prospectively to an award modified on or after the adoption date. The accounting standard will be effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. 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. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities (ASU No. 2017-12) In August 2017, the FASB issued an accounting standards update to improve financial reporting of hedging relationships, to better portray the economic results of an entity's risk management activities in the financial statements and to simplify application of hedge accounting guidance. The accounting standard eliminates certain hedge effectiveness measurement and reporting requirements and expands the types of permissible hedging strategies. The accounting standard will be effective for reporting periods beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance, to be applied retrospectively to the beginning of the fiscal year. The Company 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. Recently Adopted Accounting Standards Investments - Equity Method and Joint Ventures (ASU No. 2016-07) In March 2016, the FASB issued an accounting standards update providing new guidance for the accounting for equity method investments. The new guidance eliminates the requirement that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. In addition, the guidance requires that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. Therefore, upon qualifying for the equity method of accounting, no retroactive adjustment of the investment is required. The accounting standard became effective for reporting periods beginning after December 15, 2016. The Company adopted this accounting standard effective January 1, 2017 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Stock Compensation (ASU No. 2016-09) In March 2016, the FASB issued an accounting standards update to simplify several aspects of the accounting for share-based payment transactions, including income tax consequences, classifications of awards as either equity or liabilities and certain related classifications on the statement of cash flows. In addition, the new guidance permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated, as required prior to adoption of the accounting standards update, or recognized when they occur. The accounting standard became effective for reporting periods beginning after December 15, 2016. The Company adopted this accounting standard effective January 1, 2017 and elected to continue estimating forfeitures as required prior to adoption of the accounting standards update. The adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Amendments to the Consolidation Analysis (ASU No. 2016-17) In October 2016, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. Specifically, the amendments change the evaluation of whether a reporting entity is the primary beneficiary of a variable interest entity by changing how a reporting entity that is a single decision maker of a variable interest entity treats indirect interests in the entity held through related parties that are under common control with the reporting entity. The amendments became effective for annual periods beginning after December 15, 2016. The Company adopted this accounting standard, to be applied prospectively, effective January 1, 2017, and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows.

Acquisition

Acquisition	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Acquisition	Acquisition On August 31, 2016, the Company completed its acquisition of, and acquired all the remaining equity interest in, Axiall Corporation ("Axiall"), a Delaware corporation. Prior to the acquisition, the Company held 3.1 million shares in Axiall. Pursuant to the terms of the Agreement and Plan of Merger, dated as of June 10, 2016, by and among Westlake, Axiall and Lagoon Merger Sub, Inc., a Delaware corporation that is a wholly-owned subsidiary of Westlake ("Merger Sub"), the Company acquired all of the remaining issued and outstanding shares of common stock of Axiall for $33.00 per share in cash. Pursuant to the Merger Agreement, Merger Sub was merged with and into Axiall and Axiall survived the merger as a wholly-owned subsidiary of the Company (the "Merger"). The combined company is the third-largest global chlor-alkali producer and the third-largest global polyvinyl chloride ("PVC") producer. The Company's management believes that this strategic acquisition will enhance its strategy of integration and will further strengthen its role in the North American markets. Axiall produces a highly integrated chain of chlor-alkali and derivative products, including chlorine, caustic soda, vinyl chloride monomer ("VCM"), PVC resin, PVC compounds and chlorinated derivative products. Axiall also manufactures and sells building products, including siding, trim, mouldings, pipe and pipe fittings. Total consideration transferred for the Merger was $2,539,360 . The Merger was accounted for under the acquisition method of accounting. The assets acquired and liabilities assumed and the results of operations of the acquired business are included in the Company's Vinyls segment. For the nine months ended September 30, 2016 , the Company recognized $90,550 of transaction and integration-related costs. This included acquisition-related costs of $43,895 for advisory, consulting and professional fees and other expenses during the nine months ended September 30, 2016 . Transaction and integration-related costs also included $46,655 during the nine months ended September 30, 2016 related to the settlement of Axiall share-based awards, retention agreement costs and severance benefits provided to former Axiall employees in connection with the Merger. The following table summarizes the consideration transferred and the estimated fair value of identified assets acquired and liabilities assumed at the date of acquisition. The allocation of the consideration transferred is based on management's estimates, judgments and assumptions. When determining the fair values of assets acquired, liabilities assumed and noncontrolling interests of the acquiree, management made significant estimates, judgments and assumptions. Management estimated that consideration paid exceeded the fair value of the net assets acquired. Therefore, goodwill of $942,096 was recorded. The goodwill recognized is primarily attributable to synergies related to the Company's vinyls integration strategy that are expected to arise from the Merger. All of the goodwill is assigned to the Company's Vinyls segment. As a portion of the goodwill arising from the Merger is attributable to foreign operations, there will be a continuing foreign currency impact to goodwill in the consolidated financial statements. Final Purchase Consideration as of August 31, 2016 Closing stock purchase: Offer per share $ 33.00 Multiplied by number of shares outstanding at acquisition (in thousands of shares) 67,277 Fair value of Axiall shares outstanding purchased by the Company 2,220,141 Plus: Axiall debt repaid at acquisition 247,135 Seller's transaction costs paid by the Company (1) 47,458 Total fair value of consideration transferred 2,514,734 Fair value of Axiall share-based awards attributed to pre-combination service (2) 11,346 Additional settlement value of shares acquired 13,280 Purchase consideration 2,539,360 Fair value of previously held equity interest in Axiall (3) 102,300 Total fair value allocated to net assets acquired $ 2,641,660 _____________ (1) Transaction costs incurred by the seller included legal and advisory costs incurred for the benefit of Axiall's former shareholders and board of directors to evaluate the Company's initial Merger proposals, explore strategic alternatives and negotiate the purchase price. (2) The fair value of share-based awards attributable to pre-combination service includes the ratio of the pre-combination service performed to the original service period of the Axiall restricted share units and options, including related dividend equivalent rights. (3) Prior to the Merger, the Company owned 3.1 million shares in Axiall. The investment in Axiall was carried at estimated fair value with unrealized gains recorded as a component of accumulated other comprehensive loss in the consolidated balance sheet. The Company recognized a $49,080 gain for the investment in other income, net in the consolidated statements of operations upon gaining control. The following table summarizes the purchase price allocation: Net Assets Acquired as of August 31, 2016 Cash $ 88,251 Accounts receivable (1) 422,274 Income tax receivable 50,980 Inventories (2) 349,205 Prepaid expenses and other current assets 55,462 Property, plant and equipment (2) 2,942,162 Customer relationships (weighted average lives of 9.8 years) (3) 670,000 Other intangible assets: Trade name (weighted average lives of 6.8 years) 50,000 Technology (weighted average lives of 5.4 years) 41,500 Supply contracts and leases (weighted average lives of 6.3 years) 27,288 Other assets 93,875 Total assets acquired 4,790,997 Accounts and notes payable 254,041 Interest payable 8,154 Income tax payable 1,607 Accrued compensation 44,186 Accrued liabilities 154,290 Deferred income taxes (4) 958,304 Tax reserve non-current 3,130 Pension and other post-retirement obligations 311,106 Other liabilities 101,325 Long-term debt 1,187,290 Total liabilities assumed 3,023,433 Total identifiable net assets acquired 1,767,564 Noncontrolling interest (68,000 ) Goodwill 942,096 Total fair value allocated to net assets acquired $ 2,641,660 ______________________________ (1) The fair value of accounts receivable acquired was $422,274 , with the gross contractual amount being $434,834 . The Company expects $12,560 to be uncollectible. (2) The Company obtained additional information related to its inventories and property, plant and equipment which led to an increase in inventories of $43,047 , a decrease in property, plant and equipment of $192,579 and a corresponding increase in goodwill of $149,532 compared to the estimated fair values included in the 2016 Form 10-K. (3) The Company obtained additional information related to its customer relationship balances which led to an increase in customer relationships of $80,000 and a corresponding decrease in goodwill compared to the estimated fair values included in the 2016 Form 10-K. (4) Decreases in the estimated fair values of identified assets acquired led to a decrease in deferred income taxes of $26,824 compared to the estimated fair values included in the 2016 Form 10-K. The pro forma information for the nine months ended September 30, 2016 was as follows: Pro Forma Nine Months Ended September 30, 2016 Net sales $ 5,345,365 Net income (1) $ 277,567 Net income attributable to noncontrolling interest 16,404 Net income attributable to Westlake Chemical Corporation (1) $ 261,163 Earnings per common share attributable to Westlake Chemical Corporation Basic $ 2.01 Diluted $ 2.00 _____________ (1) The pro forma net income amounts include Axiall's historical charges recorded during the eight-month period prior to the closing of the Merger for (1) divestitures; (2) restructuring; and (3) legal and settlement claims, net, of $26,666 , $22,881 and $23,376 , respectively. These amounts have not been eliminated for pro forma purposes because they do not relate to nonrecurring, transaction specific costs related to the Merger. The pro forma amounts above have been calculated after applying the Company's accounting policies and adjusting the Axiall results to reflect (1) the increase to depreciation and amortization that would have been charged assuming the fair value adjustments to property, plant and equipment and intangible assets had been applied from January 1, 2016; (2) the elimination of net sales and cost of sales between the Company and Axiall; (3) additional pension service costs; (4) amortization of debt premium and accretion of asset retirement obligations and environmental liabilities as part of the Company's adjustments to fair value; (5) incremental interest expense that would have been incurred assuming the financing arrangements entered by the Company and repayment of a portion of Axiall's outstanding debt had occurred on January 1, 2016; (6) the elimination of transaction-related costs; and (7) an adjustment to tax-effect the aforementioned pro forma adjustments using an estimated aggregate statutory income tax rate of the jurisdictions to which the above adjustments relate. The pro forma amounts do not include any potential synergies, cost savings or other expected benefits of the Merger, are presented for illustrative purposes only and are not necessarily indicative of results that would have been achieved if the Merger had occurred as of January 1, 2016 or of future operating performance.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments Restricted Cash and Cash Equivalents The Company had restricted cash and cash equivalents of $31,682 at September 30, 2017 , which was primarily related to balances that are restricted for payment of distributions to certain of the Company's current and former employees. The Company had restricted cash and cash equivalents of $186,216 at December 31, 2016 , which was primarily related to balances deposited with and held as security by the lender under the Company's term loan facility and for distributions to certain of the Company's current and former employees. The current portion of restricted cash and cash equivalents was $8,626 and $160,527 at September 30, 2017 and December 31, 2016 , respectively. The noncurrent portion of restricted cash and cash equivalents was $23,056 and $25,689 at September 30, 2017 and December 31, 2016 , respectively, and is reflected in deferred charges and other assets, net in the consolidated balance sheets. Available-for-Sale Marketable Securities The Company had no available-for-sale securities at September 30, 2017 or at December 31, 2016 . There were no sales or maturities of available-for-sale securities during the three and nine months ended September 30, 2017 . The proceeds from sales and maturities of available-for-sale securities included in the consolidated statement of cash flows and the gross realized gains and losses included in the consolidated statement of operations for the three and nine months ended September 30, 2016 are reflected in the table below. The cost of securities sold was determined using the specific identification method. Three Months Ended September 30, Nine Months Ended September 30, 2016 2016 Proceeds from sales and maturities of securities $ 360,506 $ 662,938 Gross realized gains 52,414 53,755 Gross realized losses (13 ) (35 )

Accounts Receivable

Accounts Receivable	9 Months Ended
	Sep. 30, 2017
Accounts Receivable, Net [Abstract]
Accounts Receivable	Accounts Receivable Accounts receivable consist of the following: September 30, December 31, Trade customers $ 1,111,563 $ 819,739 Affiliates 7,601 7,982 Allowance for doubtful accounts (21,961 ) (17,991 ) 1,097,203 809,730 Federal and state taxes 16,657 90,414 Other 29,119 38,599 Accounts receivable, net $ 1,142,979 $ 938,743

Inventories

Inventories	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: September 30, December 31, Finished products $ 488,061 $ 500,861 Feedstock, additives and chemicals 213,144 216,877 Materials and supplies 133,630 83,362 Inventories $ 834,835 $ 801,100

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment As of September 30, 2017 , the Company had property, plant and equipment, net totaling $6,343,637 . 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 $116,160 and $75,143 is primarily included in cost of sales in the consolidated statements of operations for the three months ended September 30, 2017 and 2016 , respectively. Depreciation expense on property, plant and equipment of $334,545 and $189,114 is primarily included in cost of sales in the consolidated statements of operations for the nine months ended September 30, 2017 and 2016 , respectively.

Other Assets

Other Assets	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other Assets Amortization expense on intangible and other assets included in cost of sales and selling, general and administrative expenses in the consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of sales $ 10,834 $ 10,061 $ 33,121 $ 24,452 Selling, general and administrative 26,792 9,114 81,323 13,888 Total amortization expense $ 37,626 $ 19,175 $ 114,444 $ 38,340 Goodwill The gross carrying amounts of goodwill and the changes in the carrying amount of goodwill for the nine months ended September 30, 2017 were as follows: Olefins Segment Vinyls Segment Total Balance at December 31, 2016 $ 29,990 $ 916,563 $ 946,553 Goodwill acquired during the period — — — Measurement period adjustment — 54,605 54,605 Effects of changes in foreign exchange rates — 10,184 10,184 Balance at September 30, 2017 $ 29,990 $ 981,352 $ 1,011,342 The Company performed its annual impairment tests for the Vinyls reporting units in the second quarter of 2017 and did not identify any impairment.

Term Loan

Term Loan	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Term Loan	Term Loan On August 10, 2016, an indirect subsidiary of the Company, Westlake International Holdings II C.V., a limited partnership organized under the laws of the Netherlands (the "CV Borrower"), entered into a credit agreement with Bank of America, N.A., as agent and lender, providing the CV Borrower with a $150,000 term loan facility. The term loan facility had a maturity date of March 31, 2017. The term loan was fully repaid in January 2017. The loans thereunder bore interest at a floating interest rate equal to LIBOR plus 2% per annum, payable in arrears on the last day of each three-month period following the date of funding and at maturity.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consists of the following: September 30, 2017 December 31, 2016 Principal Unamortized Discount Net Principal Unamortized Net Revolving credit facility $ — $ — $ — $ 325,000 $ — $ 325,000 4.625% senior notes due 2021 (the "4.625% Westlake 2021 Senior Notes") 624,793 21,881 646,674 624,793 26,837 651,630 4.625% senior notes due 2021 (the "4.625% Subsidiary 2021 Senior Notes") 63,207 2,343 65,550 63,207 2,862 66,069 3.60% senior notes due 2022 250,000 (1,635 ) 248,365 250,000 (1,891 ) 248,109 4.875% senior notes due 2023 (the "4.875% Westlake 2023 Senior Notes") 433,793 11,791 445,584 433,793 13,431 447,224 4.875% senior notes due 2023 (the "4.875% Subsidiary 2023 Senior Notes") 16,207 477 16,684 16,207 540 16,747 3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes") 750,000 (10,031 ) 739,969 750,000 (10,757 ) 739,243 Loan related to tax-exempt waste disposal revenue bonds due 2027 10,889 — 10,889 10,889 — 10,889 6 ½% tax-exempt senior notes due 2029 100,000 (861 ) 99,139 100,000 (916 ) 99,084 6 ¾% tax-exempt senior notes due 2032 250,000 (605 ) 249,395 250,000 (1,883 ) 248,117 6 ½% tax-exempt senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes") 89,000 (806 ) 88,194 89,000 (839 ) 88,161 6 ½% tax-exempt senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes") 65,000 (578 ) 64,422 65,000 (602 ) 64,398 5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes") 700,000 (25,463 ) 674,537 700,000 (26,017 ) 673,983 Long-term debt, net $ 3,352,889 $ (3,487 ) $ 3,349,402 $ 3,677,889 $ 765 $ 3,678,654 Credit Agreement The Company has a $1,000,000 revolving credit facility that matures on August 23, 2021 (the "Credit Agreement"). The Credit Agreement bears interest at either (a) LIBOR plus a spread ranging from 1.00% to 1.75% or (b) Alternate Base Rate plus a spread ranging from 0.00% to 0.75% depending on the credit rating of the Company. At September 30, 2017 , the Company had no borrowings outstanding under the Credit Agreement. As of September 30, 2017 , the Company had outstanding letters of credit totaling $45,414 and borrowing availability of $954,586 under the Credit Agreement. As of September 30, 2017 , the Company was in compliance with the total leverage ratio financial maintenance covenant. 3.60% Senior Notes due 2026 and 5.0% Senior Notes due 2046 In August 2016, the Company issued $750,000 aggregate principal amount of 3.60% senior notes due 2026 (the " 3.60% 2026 Senior Notes ") and $700,000 aggregate principal amount of 5.0% senior notes due 2046 (the " 5.0% 2046 Senior Notes "). On March 27, 2017, the Company commenced registered exchange offers to exchange the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes for new notes that are identical in all material respects to the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes , except that the offer and issuance of the new SEC-registered notes have been registered under the Securities Act of 1933, as amended (the “Securities Act”). The exchange offers expired on April 24, 2017, and approximately 99.97% of the 3.60% 2026 Senior Notes and 100.00% of the 5.0% 2046 Senior Notes were exchanged. The 3.60% 2026 Senior Notes that were not exchanged pursuant to the exchange offers have not been registered under the Securities Act or any state securities laws and may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements or a transaction not subject to the registration requirements of the Securities Act or any state securities law. 4.625% Senior Notes due 2021 and 4.875% Senior Notes due 2023 In September 2016, the Company issued $624,793 aggregate principal amount of 4.625% senior notes due 2021 (the “ 4.625% Westlake 2021 Senior Notes ”) and $433,793 aggregate principal amount of 4.875% senior notes due 2023 (the “ 4.875% Westlake 2023 Senior Notes ”) upon the closing of the Company's offers to exchange any and all of the $688,000 aggregate principal amount of the outstanding 4.625% senior notes due 2021 issued by Eagle Spinco Inc., a wholly-owned subsidiary of Axiall (“Eagle Spinco”), and the $450,000 aggregate principal amount of the outstanding 4.875% senior notes due 2023 issued by Axiall. In the exchange offers, $624,793 aggregate principal amount of 4.625% Westlake 2021 Senior Notes and $433,793 aggregate principal amount of 4.875% Westlake 2023 Senior Notes were issued by the Company, leaving outstanding $63,207 aggregate principal amount of the 4.625% 2021 senior notes (the " 4.625% Subsidiary 2021 Senior Notes ") and $16,207 aggregate principal amount of the 4.875% 2023 senior notes (the " 4.875% Subsidiary 2023 Senior Notes "). On March 27, 2017, the Company commenced registered exchange offers to exchange the 4.625% Westlake 2021 Senior Notes and the 4.875% Westlake 2023 Senior Notes for new SEC-registered notes that are identical in all material respects to the 4.625% Westlake 2021 Senior Notes and the 4.875% Westlake 2023 Senior Notes , except that the offer and issuance of the new notes have been registered under the Securities Act. The exchange offers expired on April 24, 2017, and 100.00% of both the 4.625% Westlake 2021 Senior Notes and the 4.875% Westlake 2023 Senior Notes were exchanged. GO Zone Bonds During September 2017, the Company directed the Louisiana Local Government Authority Environmental Facilities and Community Development Authority (the “Authority”) to optionally redeem in full $250,000 aggregate principal amount of the 2007 Series revenue bonds (the “GO Zone Bonds”) on November 1, 2017. The GO Zone Bonds were issued by the Authority in December 2007 under the Gulf Opportunity Zone Act of 2005 (GO Zone Act) for the benefit of the Company and were subject to optional redemption by the Authority upon the direction of the Company at any time on or after November 1, 2017 for 100% of the principal plus accrued interest. In connection with the redemption of the Go Zone Bonds, the Authority is required to cause the GO Zone Bonds trustee to surrender the 6 ¾% tax exempt senior notes due November 2032 to the Senior Notes trustee for cancellation. The Company used cash on hand to fund the redemption of the GO Zone Bonds. As of September 30, 2017, the Company was in compliance with all of the covenants with respect to the Credit Agreement, 3.60% 2026 Senior Notes , 5.0% 2046 Senior Notes , 4.625% Westlake 2021 Senior Notes , 4.875% Westlake 2023 Senior Notes , 3.60% Senior Notes Due 2022, 6 ½% tax-exempt senior notes due 2029, the 6 ¾% tax-exempt senior notes due 2032, the 6 ½% 2035 GO Zone Senior Notes, the 6 ½% 2035 IKE Zone Senior Notes and the waste disposal revenue bonds. Unamortized debt issuance costs on Long-term debt were $21,547 and $24,113 at September 30, 2017 and December 31, 2016 , respectively.

Pension and Post-Retirement Ben

Pension and Post-Retirement Benefits	9 Months Ended
	Sep. 30, 2017
Defined Benefit Plan [Abstract]
Pension and Post-Retirement Benefits	Pension and Post-Retirement Benefits In connection with the Merger, the Company assumed certain U.S. and non-U.S. pension plans and other post-retirement benefit plans covering Axiall employees. The Axiall pension plans are closed to new participants and provide benefits to certain employees and retirees. The other post-retirement benefit plans are unfunded and provide medical and life insurance benefits for certain employees and their dependents. See Note 2 for the fair value of pension and other post-retirement obligations assumed in the Merger. Defined Benefit Plans Components of net periodic benefit cost (income) for the Company's pension plans are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. Service cost $ 1,336 $ 528 $ 315 $ 318 $ 4,007 $ 1,509 $ 315 $ 777 Expected administrative expenses — — 730 — — — 730 — Interest cost 6,198 615 2,191 622 18,594 1,754 1,553 1,763 Expected return on plan assets (9,976 ) (162 ) (3,800 ) (50 ) (29,928 ) (466 ) (5,260 ) (50 ) Amortization of net loss 297 217 338 — 892 663 978 — Net periodic benefit cost (income) $ (2,145 ) $ 1,198 $ (226 ) $ 890 $ (6,435 ) $ 3,460 $ (1,684 ) $ 2,490 The Company made $8,108 of contributions to its U.S. pension plans and $659 of contributions to its non-U.S. pension plans during the first nine months of 2017 . The Company made no contributions to its U.S. and non-U.S. pension plans during the first nine months of 2016 . 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 contributions of approximately $2,569 to its U.S. pension plans and approximately $143 to its non-U.S. pension plans during the remainder of the fiscal year ending December 31, 2017 . Other Post-retirement Benefits Components of net periodic benefit cost for the Company's other post-retirement benefits are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. Service cost $ 163 $ 14 $ 72 $ 1 $ 489 $ 41 $ 81 $ 1 Interest cost 500 35 250 3 1,499 100 540 3 Amortization of net loss 15 — 31 — 45 — 94 — Net periodic benefit cost $ 678 $ 49 $ 353 $ 4 $ 2,033 $ 141 $ 715 $ 4

Stockholders Equity

Stockholders Equity	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Changes in stockholders' equity for the nine months ended September 30, 2017 and 2016 were as follows: Common Stock Common Stock, Held in Treasury Additional Paid-in Capital Retained Earnings Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Total Balances at December 31, 2016 $ 1,347 $ (319,339 ) $ 550,641 $ 3,412,286 $ (121,306 ) $ 368,416 $ 3,892,045 Net income — — — 501,849 — 21,429 523,278 Other comprehensive income (loss), net of income taxes: Pension and other post- retirement benefits liability — — — — 1,057 (44 ) 1,013 Foreign currency translation adjustments — — — — 106,563 2,952 109,515 Other — — — — (260 ) — (260 ) Shares issued—stock- based compensation — 4,645 (2,441 ) — — — 2,204 Stock-based compensation, net of tax on stock options exercised — — 10,223 — — — 10,223 Dividends declared — — — (76,491 ) — — (76,491 ) Distributions to noncontrolling interests — — — — — (20,767 ) (20,767 ) Issuance of Westlake Chemical Partners LP common units — — — — — 110,739 110,739 Balances at September 30, 2017 $ 1,347 $ (314,694 ) $ 558,423 $ 3,837,644 $ (13,946 ) $ 482,725 $ 4,551,499 Common Stock Common Stock, Held in Treasury Additional Paid-in Capital Retained Earnings Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Total Balances at December 31, 2015 $ 1,347 $ (258,312 ) $ 542,148 $ 3,109,987 $ (129,292 ) $ 296,053 $ 3,561,931 Net income — — — 299,914 — 14,656 314,570 Other comprehensive income (loss), net of income taxes Pension and other post- retirement benefits liability — — — — 409 — 409 Foreign currency translation adjustments — — — — 15,758 — 15,758 Net unrealized holding gains on investments — — — — 4,999 — 4,999 Common stock repurchased — (66,725 ) — — — — (66,725 ) Shares issued—stock- based compensation — 5,057 (3,407 ) — — — 1,650 Stock-based compensation, net of tax on stock options exercised — — 7,778 — — — 7,778 Dividends declared — — — (71,933 ) — — (71,933 ) Distributions to noncontrolling interests — — — — — (12,300 ) (12,300 ) Noncontrolling interest in acquired business — — — — — 68,000 68,000 Balances at September 30, 2016 $ 1,347 $ (319,980 ) $ 546,519 $ 3,337,968 $ (108,126 ) $ 366,409 $ 3,824,137 Accumulated Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss) by component for the nine months ended September 30, 2017 and 2016 were as follows: Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Net Unrealized Holding Gains (Losses) on Investments, Net of Tax Total Balances at December 31, 2016 $ 28,945 $ (150,202 ) $ (49 ) $ (121,306 ) Other comprehensive income (loss) before reclassifications — 106,563 (260 ) 106,303 Amounts reclassified from accumulated other comprehensive loss 1,057 — — 1,057 Net other comprehensive income (loss) for the period 1,057 106,563 (260 ) 107,360 Balances at September 30, 2017 $ 30,002 $ (43,639 ) $ (309 ) $ (13,946 ) Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Net Unrealized Holding Gains (Losses) on Investments, Net of Tax Total Balances at December 31, 2015 $ (8,607 ) $ (115,690 ) $ (4,995 ) $ (129,292 ) Other comprehensive income (loss) before reclassifications (252 ) 15,758 57,550 73,056 Amounts reclassified from accumulated other comprehensive loss (income) 661 — (52,551 ) (51,890 ) Net other comprehensive income for the period 409 15,758 4,999 21,166 Balances at September 30, 2016 $ (8,198 ) $ (99,932 ) $ 4 $ (108,126 ) The following table provides the details of the amounts reclassified from accumulated other comprehensive income (loss) into net income in the consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 : Details about Accumulated Other Comprehensive Income (Loss) Components Location of Reclassification (Income (Expense)) in Consolidated Statements of Operations Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Amortization of pension and other post-retirement items Net loss (1) $ (529 ) $ (369 ) $ (1,600 ) $ (1,072 ) Benefit from income taxes 193 141 543 411 (336 ) (228 ) (1,057 ) (661 ) Net unrealized gains on available-for-sale investments Realized gain on available-for-sale investments Other income, net — 52,401 — 53,720 Provision for income taxes — (696 ) — (1,169 ) — 51,705 — 52,551 Total reclassifications for the period $ (336 ) $ 51,477 $ (1,057 ) $ 51,890 _____________ (1) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 13 (Employee Benefits) to the consolidated financial statements included in the 2016 Form 10-K.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2017
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 $5,972 and $1,502 for the three months ended September 30, 2017 and 2016 , respectively, and $16,740 and $6,588 for the nine months ended September 30, 2017 and 2016 , respectively. Under the Merger Agreement, all outstanding Axiall restricted stock units were assumed by the Company and converted into restricted stock units in respect of the Company's common stock, with the same terms and conditions except that upon settlement the award holders will receive the greater of (1) the value of $33.00 per Axiall restricted stock unit that was converted into a restricted stock unit in respect of the Company's common stock and (2) the value of the Company's common stock. The awards are classified as liability awards for financial accounting purposes and are re-measured at each reporting date until they vest.

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2017
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 commodities, primarily ethane and natural gas. The Company does not use derivative instruments to engage in speculative activities. The Company had no derivative instruments that were designated as fair value hedges during the three and nine months ended September 30, 2017 and 2016 . 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). The Company had non-hedge designated feedstock forward contracts for approximately 138,600,000 gallons and 12,500,000 MMBtu as of September 30, 2017 and for approximately 257,000,000 gallons and 8,500,000 MMBtu as of December 31, 2016 . Certain of the Company's derivative instruments are executed under an International Swaps and Derivatives Association ("ISDA") Master Agreement, which permits the Company and a counterparty to aggregate the amounts owed by each party under multiple transactions and replace them with a single net amount payable by one party to the other. The following tables present the Company's derivative assets and derivative liabilities reported in the consolidated balance sheets and derivative assets and derivative liabilities subject to enforceable master netting arrangements. September 30, 2017 Net Presentation Gross Presentation Net Assets (Liabilities) Presented in the Consolidated Balance Sheets Risk management assets—Commodity forward contracts Risk management liabilities—Commodity forward contracts Accounts receivable, net Derivative positions subject to enforceable master netting arrangements $ 793 $ 2,778 $ (1,985 ) Derivative positions not subject to enforceable master netting arrangements 4,557 4,557 — 5,350 7,335 (1,985 ) Deferred charges and other assets, net Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting 4,336 4,336 — 4,336 4,336 — Accrued liabilities Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting (704 ) — (704 ) (704 ) — (704 ) Other liabilities Derivative positions subject to enforceable master netting (1,410 ) 745 (2,155 ) Derivative positions not subject to enforceable master netting (2,774 ) — (2,774 ) (4,184 ) 745 (4,929 ) Risk management assets (liabilities)—Commodity forward contracts $ 12,416 $ (7,618 ) December 31, 2016 Net Presentation Gross Presentation Net Assets (Liabilities) Presented in the Consolidated Balance Sheets Risk management assets—Commodity forward contracts Risk management liabilities—Commodity forward contracts Accounts receivable, net Derivative positions subject to enforceable master netting $ 1,498 $ 1,636 $ (138 ) Derivative positions not subject to enforceable master netting 6,091 6,091 — 7,589 7,727 (138 ) Deferred charges and other assets, net Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting 5,249 5,249 — 5,249 5,249 — Accrued liabilities Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting (1,349 ) — (1,349 ) (1,349 ) — (1,349 ) Other liabilities Derivative positions subject to enforceable master netting (436 ) 2,010 (2,446 ) Derivative positions not subject to enforceable master netting (3,288 ) — (3,288 ) (3,724 ) 2,010 (5,734 ) Risk management assets (liabilities)—Commodity forward contracts $ 14,986 $ (7,221 ) The impacts 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 Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Commodity forward contracts Cost of sales $ 6,846 $ (7,840 ) $ (2,756 ) $ 7,784 See Note 14 for the fair value of the Company's derivative instruments.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
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: September 30, 2017 Level 1 Level 2 Total Derivative instruments Risk management assets—Commodity forward contracts $ 233 $ 12,183 $ 12,416 Risk management liabilities—Commodity forward contracts (6,183 ) (1,435 ) (7,618 ) December 31, 2016 Level 1 Level 2 Total Derivative instruments Risk management assets—Commodity forward contracts $ 878 $ 14,108 $ 14,986 Risk management liabilities—Commodity forward contracts (6,854 ) (367 ) (7,221 ) 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 nine months ended September 30, 2017 and 2016 . 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 current 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, accounts payable and current term loan approximate their fair values 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 fair value of the Company's long-term debt instruments is determined using a market approach, based upon quotes from financial reporting services. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy. September 30, 2017 December 31, 2016 Carrying Value Fair Value Carrying Value Fair Value Revolving credit facility $ — $ — $ 325,000 $ 325,000 4.625% Westlake 2021 Senior Notes 646,674 646,486 651,630 650,847 4.625% Subsidiary 2021 Senior Notes 65,550 62,983 66,069 65,775 3.60% senior notes due 2022 248,365 255,733 248,109 251,725 4.875% Westlake 2023 Senior Notes 445,584 452,004 447,224 451,301 4.875% Subsidiary 2023 Senior Notes 16,684 16,842 16,747 16,501 3.60% 2026 Senior Notes 739,969 749,570 739,243 722,055 Loan related to tax-exempt waste disposal revenue bonds due 2027 10,889 10,889 10,889 10,889 6 ½% tax-exempt senior notes due 2029 99,139 113,789 99,084 112,433 6 ¾% tax-exempt senior notes due 2032 249,395 251,250 248,117 258,818 6 ½% 2035 GO Zone Senior Notes 88,194 100,936 88,161 100,323 6 ½% 2035 IKE Zone Senior Notes 64,422 73,908 64,398 73,270 5.0% 2046 Senior Notes 674,537 760,739 673,983 691,712

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rate was 33.1% for the third quarter of 2017 . The effective income tax rate for the third quarter of 2017 was below the U.S. federal statutory rate of 35.0% primarily due to a higher domestic manufacturing deduction, depletion deductions, income attributable to noncontrolling interests, research and development credits and the foreign earnings rate differential, partially offset by state income taxes. The effective income tax rate, which was a benefit, was (10.3)% for three months ended September 30, 2016 . The effective income tax rate for the third quarter of 2016 was below the U.S. federal statutory rate of 35.0% primarily due to the benefit of state tax credits, the domestic manufacturing deduction, depletion deductions, income attributable to noncontrolling interests, the non-recognition of tax related to the gain recognized on previously held outstanding shares of common stock of Axiall, the benefit in prior years' and current-year tax credits for increased research and development expenditures and adjustments related to prior years' tax returns as filed and the foreign earnings rate differential, partially offset by state income taxes and nondeductible transaction costs related to the Merger. The effective income tax rate was 30.8% for the nine months ended September 30, 2017 . The effective income tax rate for the nine months ended September 30, 2017 was below the U.S. federal statutory rate of 35.0% primarily due to certain discrete adjustments, a higher domestic manufacturing deduction, depletion deductions, income attributable to noncontrolling interests, research and development credits and the foreign earnings rate differential, partially offset by state income taxes. The effective income tax rate was 29.1% for the nine months ended September 30, 2016 . The effective income tax rate for the 2016 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, depletion deductions, income attributable to noncontrolling interests, the non-recognition of tax related to the gain recognized on previously held outstanding shares of common stock of Axiall, the benefit in prior years' and current-year tax credits for increased research and development expenditures and adjustments related to prior years' tax returns as filed and the foreign earnings rate differential, partially offset by state income taxes and nondeductible transaction costs related to the Merger. The Company files income tax returns in the U.S. federal jurisdiction and in various states and foreign jurisdictions. During the second quarter of 2017, the Internal Revenue Service began an audit of the Company for the tax years 2012 to 2014.

Earnings per Share

Earnings per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The Company has unvested restricted stock units outstanding that are considered participating securities and, therefore, computes basic and diluted earnings per share under the two-class method. Basic earnings per share for the periods are based upon the weighted average number of shares of common stock outstanding during the periods. Diluted earnings per share include the effect of certain stock options. Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net income attributable to Westlake Chemical Corporation $ 210,832 $ 65,662 $ 501,849 $ 299,914 Less: Net income attributable to participating securities (1,117 ) (294 ) (2,630 ) (1,347 ) Net income attributable to common shareholders $ 209,715 $ 65,368 $ 499,219 $ 298,567 The following table reconciles the denominator for the basic and diluted earnings per share computations shown in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Weighted average common shares—basic 129,069,186 128,793,661 129,033,597 129,519,577 Plus incremental shares from: Assumed exercise of options 819,782 586,295 756,368 584,320 Weighted average common shares—diluted 129,888,968 129,379,956 129,789,965 130,103,897 Earnings per common share attributable to Westlake Chemical Corporation: Basic $ 1.62 $ 0.51 $ 3.87 $ 2.31 Diluted $ 1.61 $ 0.51 $ 3.85 $ 2.29 Excluded from the computation of diluted earnings per share are options to purchase 335,276 and 620,010 shares of common stock for the three months ended September 30, 2017 and 2016 , respectively, and 291,888 and 577,254 shares of common stock for the nine months ended September 30, 2017 and 2016 , 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	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Information	Supplemental Information Accrued Liabilities Accrued liabilities were $609,472 and $537,483 at September 30, 2017 and December 31, 2016 , respectively. Accrued rebates and accrued income taxes, which are components of accrued liabilities, were $110,862 and $72,187 , respectively, at September 30, 2017 and $77,985 and $10,891 , respectively, at December 31, 2016 . No other component of accrued liabilities was more than five percent of total current liabilities. Accrued liabilities with affiliates were $30,609 and $10,551 at September 30, 2017 and December 31, 2016 , respectively. Non-cash Investing Activity The change in capital expenditure accrual increasing additions to property, plant and equipment was $8,082 for the nine months ended September 30, 2017 . The change in capital expenditure accrual increasing additions to property, plant and equipment was $23,878 for the nine months ended September 30, 2016 . Other Income, Net Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Interest income $ 644 $ 537 $ 1,578 $ 6,900 Dividend income 127 574 250 1,499 Acquisition-related financing costs — (11,420 ) — (12,220 ) Foreign exchange currency loss, net (3,197 ) (1,281 ) (9,483 ) (2,435 ) Gain realized on previously held shares of Axiall common stock — 49,080 — 49,080 Gains from sales of securities, net — 3,321 — 4,640 Income from non-consolidated subsidiaries 3,855 1,475 11,066 7,213 Other 629 (1,021 ) 3,180 (2,586 ) Other income, net $ 2,058 $ 41,265 $ 6,591 $ 52,091

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company is involved in a number of legal and regulatory matters, principally environmental in nature, that are incidental to the normal conduct of its business, including lawsuits, investigations and claims. The outcomes of these matters are inherently unpredictable. The Company believes that, in the aggregate, the outcome of all known legal and regulatory matters will not have a material adverse effect on its consolidated financial statements; however, specific outcomes with respect to such matters may be material to the Company's consolidated statements of operations in any particular period in which costs, if any, are recognized. The Company's assessment of the potential impact of environmental matters, in particular, is subject to uncertainty due to the complex, ongoing and evolving process of investigation and remediation of such environmental matters, and the potential for technological and regulatory developments. In addition, the impact of evolving claims and programs, such as natural resource damage claims, industrial site reuse initiatives and state remediation programs creates further uncertainty of the ultimate resolution of these matters. The Company anticipates that the resolution of many legal and regulatory matters, and in particular environmental matters, will occur over an extended period of time. Environmental. As of September 30, 2017 and December 31, 2016 , the Company had reserves for environmental contingencies totaling approximately $47,409 and $48,817 , respectively, most of which was classified as noncurrent liabilities. The Company's assessment of the potential impact of these environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. From time to time the Company receives notices or inquiries from government entities regarding alleged violations of environmental laws and regulations pertaining to, among other things, the disposal, emission and storage of chemical substances, including hazardous wastes. Item 103 of the SEC's Regulation S-K requires disclosure of certain environmental matters when a governmental authority is a party to the proceedings and the proceedings involve potential monetary sanctions, unless the Company reasonably believes such sanctions would not exceed $100. • In May 2013, an amendment to an existing consent order agreed to by the West Virginia Department of Environmental Protection and a predecessor of Axiall required that it, among other things, pay a penalty in the amount of $449 and continue certain corrective action associated with discharges of hexachlorocyclohexane (commonly referred to as BHC) from the Natrium, West Virginia facility's effluent discharge outfalls. The penalty was paid and corrective actions required are on-going per a December 2016 agreement to extend the compliance date under the amended consent order. • In May 2013 and September 2013, the Environmental Protection Agency (the "EPA") conducted inspections at the Company's Plaquemine, Louisiana facility pursuant to requirements of the federal Clean Air Act Section 112(r) Risk Management Program and Title V. As a result of the inspections, the EPA identified areas of concern and the Company subsequently engaged in negotiations to resolve alleged violations. A Consent Agreement and Final Order (“CAFO”) was filed in October 2016, pursuant to which the Company paid civil penalties in the amount of $167 . • The LDEQ has issued notices of violations ("NOVs") regarding the Company's olefins facilities in Lake Charles, Louisiana for various air and water compliance issues. The Company has reached an agreement with the LDEQ to settle certain of the NOVs along with other alleged violations not made the subject of any specific NOV in two separate settlement agreements, pursuant to which the Company paid $192 in civil penalties. • During September 2010, the Company's vinyls facilities in north Lake Charles and Plaquemine each received a Consolidated Compliance Order and Notice of Potential Penalty, alleging violations of various requirements of those facilities' air permits, based largely on self-reported permit deviations related to record-keeping violations. The Company has been negotiating a possible global settlement of these and several other matters with the LDEQ. The Company believes the resolution of these matters may require the payment of a monetary sanction in excess of $100 . • In April 2015, Axiall received a communication from the EPA related to, among other things, the EPA's investigation of the 2012 and 2013 fires that occurred at its VCM plant in Lake Charles. In late 2015, Axiall settled this matter with the EPA, with such settlement including on-going supplemental environmental projects and a penalty payment of $878 . • For several years, the EPA has been conducting an enforcement initiative against petroleum refineries and petrochemical plants with respect to emissions from flares. 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, Kentucky and certain Lake Charles 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 indicated that it is seeking a consent decree that would obligate the Company to take corrective actions relating to the alleged noncompliance. The Company believes the resolution of these matters may require the payment of a monetary sanction in excess of $100 . The Company does not believe that resolutions of any or all of these matters will have a material adverse effect on the Company's financial condition, results of operations or cash flows. Environmental Remediation: Reasonably Possible Matters. The Company's assessment of the potential impact of environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. As such, in addition to the amounts currently reserved, the Company may be subject to reasonably possible loss contingencies related to environmental matters in the range of $40,000 to $80,000 . Commitments. In connection with the Merger, the Company became a party to a joint venture investment with Lotte Chemical USA Corporation to build an ethylene facility, LACC, LLC ("LACC"). The ethylene facility is located adjacent to the Company's vinyls facility in Lake Charles. Pursuant to the contribution and subscription agreement, the Company agreed to make a maximum capital commitment to LACC of up to $225,000 to fund the construction costs of the ethylene plant, which represents approximately 10.0% of the interests in LACC. The construction of the ethylene plant commenced in January 2016, with an anticipated start-up in 2019. As of September 30, 2017 , the Company had funded approximately $106,405 of the Company's portion of the construction costs of the ethylene plant.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2017
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 September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net external sales Olefins Polyethylene $ 377,269 $ 380,810 $ 1,121,603 $ 1,098,500 Styrene, feedstock and other 124,974 116,555 412,869 324,369 Total Olefins 502,243 497,365 1,534,472 1,422,869 Vinyls PVC, caustic soda and other 1,252,963 599,276 3,541,409 1,492,650 Building products 353,683 182,387 954,785 424,757 Total Vinyls 1,606,646 781,663 4,496,194 1,917,407 $ 2,108,889 $ 1,279,028 $ 6,030,666 $ 3,340,276 Intersegment sales Olefins $ 106,722 $ 30,614 $ 290,658 $ 85,856 Vinyls 260 2,130 871 2,719 $ 106,982 $ 32,744 $ 291,529 $ 88,575 Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income (loss) from operations Olefins $ 165,438 $ 118,475 $ 488,532 $ 408,274 Vinyls 216,515 22,235 431,276 136,559 Corporate and other (16,206 ) (94,147 ) (51,647 ) (116,056 ) $ 365,747 $ 46,563 $ 868,161 $ 428,777 Depreciation and amortization Olefins $ 35,029 $ 36,649 $ 111,244 $ 95,582 Vinyls 117,490 56,136 331,585 128,691 Corporate and other 1,115 1,444 5,704 2,920 $ 153,634 $ 94,229 $ 448,533 $ 227,193 Other income (expense), net Olefins $ (184 ) $ 1,101 $ 1,555 $ 3,706 Vinyls (970 ) (1,226 ) 1,087 1,722 Corporate and other 3,212 41,390 3,949 46,663 $ 2,058 $ 41,265 $ 6,591 $ 52,091 Provision for (benefit from) income taxes Olefins $ 58,218 $ 31,956 $ 152,482 $ 136,429 Vinyls 60,784 (3,912 ) 114,979 29,655 Corporate and other (10,383 ) (34,596 ) (34,771 ) (36,752 ) $ 108,619 $ (6,552 ) $ 232,690 $ 129,332 Capital expenditures Olefins $ 20,960 $ 96,469 $ 70,043 $ 285,359 Vinyls 107,515 83,523 329,968 180,392 Corporate and other 4,894 178 14,260 1,579 $ 133,369 $ 180,170 $ 414,271 $ 467,330 A reconciliation of total segment income from operations to consolidated income before income taxes is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income from operations $ 365,747 $ 46,563 $ 868,161 $ 428,777 Interest expense (40,036 ) (24,366 ) (118,784 ) (36,966 ) Other income (expense), net 2,058 41,265 6,591 52,091 Income before income taxes $ 327,769 $ 63,462 $ 755,968 $ 443,902 September 30, December 31, Total assets Olefins $ 2,015,888 $ 2,092,617 Vinyls 8,695,509 8,287,204 Corporate and other 532,728 510,432 $ 11,244,125 $ 10,890,253

Westlake Chemical Partners Offe

Westlake Chemical Partners Offerings	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Westlake Chemical Partners LP Offerings	Westlake Chemical Partners LP Offerings In March 2014, we formed Westlake Chemical Partners LP ("WLKP") to operate, acquire and develop ethylene production facilities and related assets. On August 4, 2014, WLKP completed its initial public offering (the "IPO") of 12,937,500 common units at a price of $24.00 per unit. Net proceeds to WLKP from the sale of the units was approximately $286,100 , net of underwriting discounts, structuring fees and estimated offering expenses of approximately $24,400 . At the consummation of the IPO, WLKP's assets consisted of a 10.6% limited partner interest in Westlake Chemical OpCo LP ("OpCo"), as well as the general partner interest in OpCo. Immediately after the IPO, the Company retained an 89.4% limited partner interest in OpCo and a significant interest in WLKP. The initial public offering represented the sale of 47.8% of the common units in WLKP. On April 29, 2015, WLKP purchased an additional 2.7% newly-issued limited partner interest in OpCo. On September 29, 2017, WLKP purchased an additional 5.0% newly-issued limited partner interest in OpCo. On September 29, 2017, WLKP completed a secondary offering of 5,175,000 common units at a price of $22.00 per unit. Net proceeds to WLKP from the sale of the units was $110,739 , net of underwriting discounts, structuring fees and estimated offering expenses of approximately $3,111 . At September 30, 2017, WLKP had a 18.3% limited partner interest in OpCo, and the Company retained a 81.7% limited partner interest in OpCo and a significant interest in WLKP.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent events were evaluated through the date on which the consolidated financial statements were issued.

Guarantor Disclosures

Guarantor Disclosures	9 Months Ended
	Sep. 30, 2017
Guarantees [Abstract]
Guarantor Disclosures	Guarantor Disclosures The Company's payment obligations under the 3.60% senior notes due 2022 , the 3.60% 2026 Senior Notes, the 5.0% 2046 Senior Notes, 4.625% Westlake 2021 Senior Notes and the 4.875% Westlake 2023 Senior Notes 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 those notes in excess of $5,000 (the "Guarantor Subsidiaries"). Each Guarantor Subsidiary is 100% owned by Westlake Chemical Corporation (the " 100% Owned Guarantor Subsidiaries"). In October 2016, the Company executed a Joinder Agreement with the Administrative Agent of the Credit Agreement, whereby certain subsidiaries of the Company were added as Guarantor Subsidiaries. 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, and the remaining subsidiaries that do not guarantee the 3.60% senior notes due 2022 , the 3.60% 2026 Senior Notes, the 5.0% 2046 Senior Notes, 4.625% Westlake 2021 Senior Notes and the 4.875% Westlake 2023 Senior Notes (the "Non-Guarantor Subsidiaries"), together with consolidating eliminations necessary to present the Company's results on a consolidated basis. In August 2016, certain of the Company's subsidiary guarantors were released from their guarantees of the Company's 3.60% senior notes due 2022 in connection with the replacement of the Company's revolving credit facility. Westlake Chemical OpCo LP, which was previously separately presented as a less than 100% owned guarantor, and certain of the Company's other 100% owned subsidiaries that were previously presented as guarantors, are now reflected as Non-Guarantor Subsidiaries in the condensed consolidating guarantor financial information. Prior periods were retrospectively adjusted to conform to the current presentation of Guarantor Subsidiaries and Non-Guarantor Subsidiaries. Condensed Consolidating Financial Information as of September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Balance Sheet Current assets Cash and cash equivalents $ 334,111 $ 33,089 $ 311,033 $ — $ 678,233 Accounts receivable, net 3,060,591 4,048,824 432,238 (6,398,674 ) 1,142,979 Inventories — 631,322 203,513 — 834,835 Prepaid expenses and other current assets 16,616 31,785 22,365 (35,906 ) 34,860 Restricted cash — 1,275 7,351 — 8,626 Total current assets 3,411,318 4,746,295 976,500 (6,434,580 ) 2,699,533 Property, plant and equipment, net — 4,330,104 2,013,533 — 6,343,637 Other assets, net Goodwill — 854,896 156,446 — 1,011,342 Customer relationships, net — 493,960 141,924 — 635,884 Other intangible assets, net — 92,155 74,011 — 166,166 Deferred charges and other assets, net 9,890,164 551,732 1,372,070 (11,426,403 ) 387,563 Total other assets, net 9,890,164 1,992,743 1,744,451 (11,426,403 ) 2,200,955 Total assets $ 13,301,482 $ 11,069,142 $ 4,734,484 $ (17,860,983 ) $ 11,244,125 Current liabilities Accounts payable $ 5,821,323 $ 830,824 $ 128,673 $ (6,220,016 ) $ 560,804 Accrued liabilities 155,106 436,816 232,114 (214,564 ) 609,472 Total current liabilities 5,976,429 1,267,640 360,787 (6,434,580 ) 1,170,276 Long-term debt, net 3,256,280 4,334,142 223,578 (4,464,598 ) 3,349,402 Deferred income taxes — 1,577,209 106,587 (22,882 ) 1,660,914 Pension and other liabilities — 364,011 148,023 — 512,034 Total liabilities 9,232,709 7,543,002 838,975 (10,922,060 ) 6,692,626 Total Westlake Chemical Corporation stockholders' equity 4,068,773 3,526,140 3,412,784 (6,938,923 ) 4,068,774 Noncontrolling interests — — 482,725 — 482,725 Total equity 4,068,773 3,526,140 3,895,509 (6,938,923 ) 4,551,499 Total liabilities and equity $ 13,301,482 $ 11,069,142 $ 4,734,484 $ (17,860,983 ) $ 11,244,125 Condensed Consolidating Financial Information as of December 31, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Balance Sheet Current assets Cash and cash equivalents $ 146,990 $ 53,006 $ 259,457 $ — $ 459,453 Accounts receivable, net 2,117,540 3,329,871 323,931 (4,832,599 ) 938,743 Inventories — 597,819 203,281 — 801,100 Prepaid expenses and other current assets 30,748 41,755 12,494 (36,504 ) 48,493 Restricted cash — — 160,527 — 160,527 Total current assets 2,295,278 4,022,451 959,690 (4,869,103 ) 2,408,316 Property, plant and equipment, net — 4,475,943 1,944,119 — 6,420,062 Other assets, net Goodwill — 791,706 154,847 — 946,553 Customer relationships, net — 468,645 142,970 — 611,615 Other intangible assets, net — 130,243 71,177 (25,581 ) 175,839 Deferred charges and other assets, net 9,170,042 874,003 1,115,877 (10,832,054 ) 327,868 Total other assets, net 9,170,042 2,264,597 1,484,871 (10,857,635 ) 2,061,875 Total assets $ 11,465,320 $ 10,762,991 $ 4,388,680 $ (15,726,738 ) $ 10,890,253 Current liabilities Accounts payable $ 4,330,375 $ 748,364 $ 225,300 $ (4,807,780 ) $ 496,259 Accrued liabilities 26,367 389,216 183,223 (61,323 ) 537,483 Term loan — — 149,341 — 149,341 Total current liabilities 4,356,742 1,137,580 557,864 (4,869,103 ) 1,183,083 Long-term debt, net 3,584,949 4,090,775 — (3,997,070 ) 3,678,654 Deferred income taxes — 1,581,260 91,809 (22,494 ) 1,650,575 Pension and other liabilities — 360,622 125,274 — 485,896 Total liabilities 7,941,691 7,170,237 774,947 (8,888,667 ) 6,998,208 Total Westlake Chemical Corporation stockholders' equity 3,523,629 3,592,754 3,245,317 (6,838,071 ) 3,523,629 Noncontrolling interests — — 368,416 — 368,416 Total equity 3,523,629 3,592,754 3,613,733 (6,838,071 ) 3,892,045 Total liabilities and equity $ 11,465,320 $ 10,762,991 $ 4,388,680 $ (15,726,738 ) $ 10,890,253 Condensed Consolidating Financial Information for the Three Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 1,704,086 $ 837,536 $ (432,733 ) $ 2,108,889 Cost of sales — 1,371,813 665,124 (426,100 ) 1,610,837 Gross profit — 332,273 172,412 (6,633 ) 498,052 Selling, general and administrative expenses 1,509 93,149 37,617 (6,633 ) 125,642 Transaction and integration-related costs — 6,387 276 — 6,663 Income (loss) from operations (1,509 ) 232,737 134,519 — 365,747 Other income (expense) Interest expense (38,811 ) (44,381 ) (1,635 ) 44,791 (40,036 ) Other income, net 37,563 2,517 6,769 (44,791 ) 2,058 Income (loss) before income taxes (2,757 ) 190,873 139,653 — 327,769 Provision for (benefit from) income taxes (599 ) 92,597 16,621 — 108,619 Equity in net income of subsidiaries 212,989 — — (212,989 ) — Net income 210,831 98,276 123,032 (212,989 ) 219,150 Net income attributable to noncontrolling interests — — 8,318 — 8,318 Net income attributable to Westlake Chemical Corporation $ 210,831 $ 98,276 $ 114,714 $ (212,989 ) $ 210,832 Comprehensive income attributable to Westlake Chemical Corporation $ 254,400 $ 98,455 $ 158,160 $ (256,615 ) $ 254,400 Condensed Consolidating Financial Information for the Three Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 984,937 $ 611,983 $ (317,892 ) $ 1,279,028 Cost of sales — 892,198 497,460 (312,763 ) 1,076,895 Gross profit — 92,739 114,523 (5,129 ) 202,133 Selling, general and administrative expenses 2,092 47,952 27,814 (5,129 ) 72,729 Transactions and integration-related costs — 82,687 154 — 82,841 Income (loss) from operations (2,092 ) (37,900 ) 86,555 — 46,563 Other income (expense) Interest expense (22,130 ) (22,207 ) (908 ) 20,879 (24,366 ) Other income (expense), net 35,405 (15,189 ) 41,928 (20,879 ) 41,265 Income (loss) before income taxes 11,183 (75,296 ) 127,575 — 63,462 Provision for (benefit from) income taxes (2,088 ) (11,080 ) 6,616 — (6,552 ) Equity in net income of subsidiaries 52,391 — — (52,391 ) — Net income 65,662 (64,216 ) 120,959 (52,391 ) 70,014 Net income attributable to noncontrolling interests — — 4,352 — 4,352 Net income attributable to Westlake Chemical Corporation $ 65,662 $ (64,216 ) $ 116,607 $ (52,391 ) $ 65,662 Comprehensive income attributable to Westlake Chemical Corporation $ 39,636 $ (64,113 ) $ 104,129 $ (40,015 ) $ 39,637 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 4,880,682 $ 2,377,862 $ (1,227,878 ) $ 6,030,666 Cost of sales — 4,077,633 1,889,571 (1,207,567 ) 4,759,637 Gross profit — 803,049 488,291 (20,311 ) 1,271,029 Selling, general and administrative expenses 2,429 281,412 116,389 (20,311 ) 379,919 Transaction and integration-related costs — 22,611 338 — 22,949 Income (loss) from operations (2,429 ) 499,026 371,564 — 868,161 Other income (expense) Interest expense (115,156 ) (133,048 ) (5,623 ) 135,043 (118,784 ) Other income, net 112,002 2,944 26,688 (135,043 ) 6,591 Income (loss) before income taxes (5,583 ) 368,922 392,629 — 755,968 Provision for (benefit from) income taxes (1,451 ) 198,054 36,087 — 232,690 Equity in net income of subsidiaries 505,981 — — (505,981 ) — Net income 501,849 170,868 356,542 (505,981 ) 523,278 Net income attributable to noncontrolling interests — — 21,429 — 21,429 Net income attributable to Westlake Chemical Corporation $ 501,849 $ 170,868 $ 335,113 $ (505,981 ) $ 501,849 Comprehensive income attributable to Westlake Chemical Corporation $ 613,350 $ 171,413 $ 233,030 $ (404,443 ) $ 613,350 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 2,567,232 $ 1,734,611 $ (961,567 ) $ 3,340,276 Cost of sales — 2,233,395 1,353,764 (945,967 ) 2,641,192 Gross profit — 333,837 380,847 (15,600 ) 699,084 Selling, general and administrative expenses 3,648 121,261 70,448 (15,600 ) 179,757 Transaction and integration-related costs — 90,396 154 — 90,550 Income (loss) from operations (3,648 ) 122,180 310,245 — 428,777 Other income (expense) Interest expense (43,228 ) (39,693 ) (1,054 ) 47,009 (36,966 ) Other income (expense), net 40,807 (22,291 ) 80,584 (47,009 ) 52,091 Income (loss) before income taxes (6,069 ) 60,196 389,775 — 443,902 Provision for (benefit from) income taxes (8,268 ) 106,792 30,808 — 129,332 Equity in net income of subsidiaries 297,715 — — (297,715 ) — Net income 299,914 (46,596 ) 358,967 (297,715 ) 314,570 Net income attributable to noncontrolling interests — — 14,656 — 14,656 Net income attributable to Westlake Chemical Corporation $ 299,914 $ (46,596 ) $ 344,311 $ (297,715 ) $ 299,914 Comprehensive income attributable to Westlake Chemical Corporation $ 321,079 $ (46,187 ) $ 364,402 $ (318,214 ) $ 321,080 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Cash Flows Cash flows from operating activities Net income $ 501,849 $ 170,868 $ 356,542 $ (505,981 ) $ 523,278 Adjustments to reconcile net income to net cash provided by (used for) operating activities Depreciation and amortization — 294,227 154,306 — 448,533 Deferred income taxes (217 ) 20,299 3,212 — 23,294 Net changes in working capital and other (532,120 ) (129,330 ) 123,028 505,981 (32,441 ) Net cash provided by (used for) operating activities (30,488 ) 356,064 637,088 — 962,664 Cash flows from investing activities Additions to property, plant and equipment — (294,138 ) (120,133 ) — (414,271 ) Additions to cost method investment — (47,000 ) — — (47,000 ) Proceeds from disposition of assets — 25 146 — 171 Proceeds from involuntary conversion of assets — — 1,672 — 1,672 Receivable under the investment management agreement — — (119,000 ) 119,000 — Settlements of derivative instruments — (7 ) — — (7 ) Net cash used for investing activities — (341,120 ) (237,315 ) 119,000 (459,435 ) Cash flows from financing activities Intercompany financing 498,272 (313,276 ) (184,996 ) — — Receivable under the investment management agreement 119,000 — — (119,000 ) — Debt issuance costs (376 ) — — — (376 ) Dividends paid (76,491 ) — — — (76,491 ) Distributions to noncontrolling interests — 279,203 (299,970 ) — (20,767 ) Net proceeds from issuance of Westlake Chemical Partners LP common units — — 110,739 — 110,739 Proceeds from issuance of notes payable — — 5,946 — 5,946 Proceeds from drawdown of revolver 225,000 — — — 225,000 Restricted cash associated with term loan — — 154,000 — 154,000 Repayment of term loan — — (150,000 ) — (150,000 ) Repayment of notes payable — (788 ) (5,907 ) — (6,695 ) Repayment of revolver (550,000 ) — — — (550,000 ) Other 2,204 — — — 2,204 Net cash provided by (used for) financing activities 217,609 (34,861 ) (370,188 ) (119,000 ) (306,440 ) Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Effect of exchange rate changes on cash and cash equivalents — — 21,991 — 21,991 Net increase (decrease) in cash and cash equivalents 187,121 (19,917 ) 51,576 — 218,780 Cash and cash equivalents at beginning of period 146,990 53,006 259,457 — 459,453 Cash and cash equivalents at end of period $ 334,111 $ 33,089 $ 311,033 $ — $ 678,233 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Cash Flows Cash flows from operating activities Net income $ 299,914 $ (46,596 ) $ 358,967 $ (297,715 ) $ 314,570 Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities Depreciation and amortization — 118,645 108,548 — 227,193 Deferred income taxes (5,178 ) 100,908 10,180 — 105,910 Net changes in working capital and other (313,676 ) (39,859 ) (47,693 ) 297,715 (103,513 ) Net cash provided by (used for) operating activities (18,940 ) 133,098 430,002 — 544,160 Cash flows from investing activities Acquisition of business, net of cash acquired — (2,437,829 ) — — (2,437,829 ) Additions to property, plant and equipment — (162,288 ) (305,042 ) — (467,330 ) Additions to cost method investment — (4,000 ) — — (4,000 ) Proceeds from disposition of assets — 48 165 — 213 Proceeds from sales and maturities of securities 658,338 — 4,600 — 662,938 Purchase of securities (138,422 ) — — — (138,422 ) Settlements of derivative instruments — (4,655 ) — — (4,655 ) Net cash provided by (used for) investing activities 519,916 (2,608,724 ) (300,277 ) — (2,389,085 ) Cash flows from financing activities Intercompany financing (2,242,604 ) 2,289,200 (46,596 ) — — Debt issuance costs (33,617 ) — (1,590 ) — (35,207 ) Dividends paid (71,933 ) — — — (71,933 ) Distributions to noncontrolling interests — 202,210 (214,510 ) — (12,300 ) Proceeds from debt issuance 1,428,512 — — — 1,428,512 Proceeds from issuance of notes payable — — 5,597 — 5,597 Proceeds from term loan and drawdown of revolver 450,000 — 150,000 — 600,000 Restricted cash associated with term loan — — (154,000 ) — (154,000 ) Repayment of notes payable — — (10,602 ) — (10,602 ) Repayment of revolver (125,000 ) — — — (125,000 ) Repurchase of common stock for treasury (67,406 ) — — — (67,406 ) Other 2,840 — — — 2,840 Net cash provided by (used for) financing activities (659,208 ) 2,491,410 (271,701 ) — 1,560,501 Effect of exchange rate changes on cash and cash equivalents — — 2,418 — 2,418 Net increase (decrease) in cash and cash equivalents (158,232 ) 15,784 (139,558 ) — (282,006 ) Cash and cash equivalents at beginning of period 303,131 6,818 352,576 — 662,525 Cash and cash equivalents at end of period $ 144,899 $ 22,602 $ 213,018 $ — $ 380,519

Basis of Financial Statements (

Basis of Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2017
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, 2016 consolidated financial statements and notes thereto of Westlake Chemical Corporation (the "Company") included in the annual report on Form 10-K for the fiscal year ended December 31, 2016 (the " 2016 Form 10-K"), filed with the SEC on February 22, 2017 . These consolidated financial statements have been prepared in conformity with the accounting principles and practices as disclosed in the notes to the consolidated financial statements of the Company for the fiscal year ended December 31, 2016 . In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of September 30, 2017 , its results of operations for the three and nine months ended September 30, 2017 and 2016 and the changes in its cash position for the nine months ended September 30, 2017 and 2016 . 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, 2017 or any other interim period. The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Revenue from Contracts with Customers (ASU No. 2014-09) 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. In 2016, the FASB issued various additional authoritative guidance for the new revenue recognition standard. The accounting standard will be effective for reporting periods beginning after December 15, 2017. The Company is in the process of evaluating the impact that the new accounting standard will have on its consolidated financial position, results of operations and cash flows. The Company has completed a preliminary assessment including detailed review of a representative sample of contracts with customers. The Company does not believe that adoption of the new accounting standard will materially impact timing or amounts of revenue recognized for the majority of its sales. The Company intends to elect the modified retrospective method of adoption. Recognition and Measurement of Financial Assets and Financial Liabilities (ASU No. 2016-01) In January 2016, the FASB issued an accounting standards update making certain changes principally to the current guidance for equity investments, financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. Among other things, the guidance (1) requires equity investments (except those accounted for under the equity method of accounting or those that result in consolidation of the investee) to be measured at fair value, with changes in fair value recognized in net income; (2) provide entities with a policy election to record equity investments without readily determinable fair values at cost, less impairment, and subsequent adjustments for observable price changes (changes in the basis of these equity investments to be reported in net income); (3) requires an entity that has elected the fair value option for financial liabilities to recognize changes in fair value due to instrument-specific credit risk separately in other comprehensive income; (4) clarified current guidance related to the valuation allowance assessment when recognizing deferred tax assets resulting from unrealized losses on available-for-sale debt securities; and (5) requires specific disclosure pertaining to financial assets and financial liabilities in the financial statements. The accounting standard will be effective for reporting periods beginning after December 15, 2017. 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. Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on a new lease standard that will supersede the existing lease guidance. The standard requires a lessee to recognize assets and liabilities related to long-term leases that are classified as operating leases under current guidance on its balance sheet. An asset would be recognized related to the right to use the underlying asset and a liability would be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures related to leases. The accounting standard will be effective for reporting periods beginning after December 15, 2018. The Company is in the process of evaluating the impact that the new accounting guidance will have on the Company's consolidated financial position, results of operations and cash flows. Credit Losses (ASU No. 2016-13) In June 2016, the FASB issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-15) In August 2016, the FASB issued an accounting standards update providing new guidance on the classification of certain cash receipts and payments including debt extinguishment costs, debt prepayment costs, settlement of zero-coupon debt instruments, contingent consideration payments, proceeds from the settlement of insurance claims and life insurance policies and distributions received from equity method investees in the statement of cash flows. This update is required to be applied using the retrospective transition method to each period presented unless it is impracticable to be applied retrospectively. In such situation, this guidance is to be applied prospectively. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Cash Flows (ASU No. 2016-18) In November 2016, the FASB issued an accounting standards update to clarify certain existing principles in Accounting Standards Codification ("ASC") 230, Cash flows, including providing additional guidance related to transfers between cash and restricted cash and how entities present, in their statement of cash flows, the cash receipts and cash payments that directly affect the restricted cash accounts. The accounting standard will be effective for reporting periods beginning after December 15, 2017. Upon adoption of the accounting standards update, the Company will retrospectively adjust its financial statements to reflect restricted cash in the beginning and ending cash and restricted cash balances within the statements of cash flows. Transfers between cash and restricted cash will be excluded from net changes in cash and cash equivalents within the statements of cash flows. Business Combinations (ASU No. 2017-01) In January 2017, the FASB issued an accounting standards update to assist entities with evaluating when a set of transferred assets and activities is a business. The guidance requires an entity to evaluate if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets; if so, the set of transferred assets and activities is not a business. The guidance also requires a business to include at least one substantive process and narrows the definition of outputs by more closely aligning it with how outputs are described in the ASC 606, Revenue from contracts with customers. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Other Income - Gains and Losses from the Derecognition of Nonfinancial Assets (ASU No. 2017-05) In February 2017, the FASB issued an accounting standards update to clarify the scope of guidance related to other income — gains and losses from the derecognition of nonfinancial assets, and to add guidance for partial sales of nonfinancial assets. The new guidance clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. The guidance also outlines that when an entity transfers its controlling interest in a nonfinancial asset, but retains a noncontrolling interest, it will measure the retained interest at fair value resulting in full gain or loss recognition upon sale of the controlling interest. The accounting standard will be effective for reporting periods beginning after December 15, 2017 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Compensation - Retirement Benefits (ASU No. 2017-07) In March 2017, the FASB issued an accounting standards update to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The new guidance requires employers to disaggregate the service cost component from the other components of net periodic benefit cost and report the service cost component in the same line item or items as other compensation costs arising from services rendered by the pertinent employees during the period. The amendments also allow only the service cost component to be eligible for capitalization when applicable. The accounting standard will be effective for reporting periods beginning after December 15, 2017. 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. Compensation - Stock Compensation (ASU No. 2017-09) In May 2017, the FASB issued the accounting standards update to provide clarity and reduce both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, Compensation-Stock Compensation, to a change to the terms or conditions of a share-based payment award. The amendments in this update provide guidance about which changes to the terms or conditions of a share-based payment award require the application of modification accounting in Topic 718. Essentially, an entity will not have to account for the effects of a modification if: (1) the fair value of the modified award is the same immediately before and after the modification; (2) the vesting conditions of the modified award are the same immediately before and after the modification; and (3) the classification of the modified award as either an equity instrument or liability instrument is the same immediately before and after the modification. This update is to be applied prospectively to an award modified on or after the adoption date. The accounting standard will be effective for reporting periods beginning after December 15, 2017. Early adoption is permitted. 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. Derivatives and Hedging - Targeted Improvements to Accounting for Hedging Activities (ASU No. 2017-12) In August 2017, the FASB issued an accounting standards update to improve financial reporting of hedging relationships, to better portray the economic results of an entity's risk management activities in the financial statements and to simplify application of hedge accounting guidance. The accounting standard eliminates certain hedge effectiveness measurement and reporting requirements and expands the types of permissible hedging strategies. The accounting standard will be effective for reporting periods beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance, to be applied retrospectively to the beginning of the fiscal year. The Company 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. Recently Adopted Accounting Standards Investments - Equity Method and Joint Ventures (ASU No. 2016-07) In March 2016, the FASB issued an accounting standards update providing new guidance for the accounting for equity method investments. The new guidance eliminates the requirement that when an investment qualifies for use of the equity method as a result of an increase in the level of ownership interest or degree of influence, an investor must adjust the investment, results of operations and retained earnings retroactively on a step-by-step basis as if the equity method had been in effect during all previous periods that the investment had been held. In addition, the guidance requires that the equity method investor add the cost of acquiring the additional interest in the investee to the current basis of the investor's previously held interest and adopt the equity method of accounting as of the date the investment becomes qualified for equity method accounting. Therefore, upon qualifying for the equity method of accounting, no retroactive adjustment of the investment is required. The accounting standard became effective for reporting periods beginning after December 15, 2016. The Company adopted this accounting standard effective January 1, 2017 and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Stock Compensation (ASU No. 2016-09) In March 2016, the FASB issued an accounting standards update to simplify several aspects of the accounting for share-based payment transactions, including income tax consequences, classifications of awards as either equity or liabilities and certain related classifications on the statement of cash flows. In addition, the new guidance permits entities to make an accounting policy election for the impact of forfeitures on the recognition of expense for share-based payment awards. Forfeitures can be estimated, as required prior to adoption of the accounting standards update, or recognized when they occur. The accounting standard became effective for reporting periods beginning after December 15, 2016. The Company adopted this accounting standard effective January 1, 2017 and elected to continue estimating forfeitures as required prior to adoption of the accounting standards update. The adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows. Amendments to the Consolidation Analysis (ASU No. 2016-17) In October 2016, the FASB issued an accounting standards update making certain changes to the current consolidation guidance. The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. Specifically, the amendments change the evaluation of whether a reporting entity is the primary beneficiary of a variable interest entity by changing how a reporting entity that is a single decision maker of a variable interest entity treats indirect interests in the entity held through related parties that are under common control with the reporting entity. The amendments became effective for annual periods beginning after December 15, 2016. The Company adopted this accounting standard, to be applied prospectively, effective January 1, 2017, and the adoption did not have a material impact on the Company's consolidated financial position, results of operations and cash flows.

Acquisition (Tables)

Acquisition (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information	The pro forma information for the nine months ended September 30, 2016 was as follows: Pro Forma Nine Months Ended September 30, 2016 Net sales $ 5,345,365 Net income (1) $ 277,567 Net income attributable to noncontrolling interest 16,404 Net income attributable to Westlake Chemical Corporation (1) $ 261,163 Earnings per common share attributable to Westlake Chemical Corporation Basic $ 2.01 Diluted $ 2.00 _____________ (1) The pro forma net income amounts include Axiall's historical charges recorded during the eight-month period prior to the closing of the Merger for (1) divestitures; (2) restructuring; and (3) legal and settlement claims, net, of $26,666 , $22,881 and $23,376 , respectively. These amounts have not been eliminated for pro forma purposes because they do not relate to nonrecurring, transaction specific costs related to the Merger.
Schedule of Business Acquisitions	The following table summarizes the consideration transferred and the estimated fair value of identified assets acquired and liabilities assumed at the date of acquisition. The allocation of the consideration transferred is based on management's estimates, judgments and assumptions. When determining the fair values of assets acquired, liabilities assumed and noncontrolling interests of the acquiree, management made significant estimates, judgments and assumptions. Management estimated that consideration paid exceeded the fair value of the net assets acquired. Therefore, goodwill of $942,096 was recorded. The goodwill recognized is primarily attributable to synergies related to the Company's vinyls integration strategy that are expected to arise from the Merger. All of the goodwill is assigned to the Company's Vinyls segment. As a portion of the goodwill arising from the Merger is attributable to foreign operations, there will be a continuing foreign currency impact to goodwill in the consolidated financial statements. Final Purchase Consideration as of August 31, 2016 Closing stock purchase: Offer per share $ 33.00 Multiplied by number of shares outstanding at acquisition (in thousands of shares) 67,277 Fair value of Axiall shares outstanding purchased by the Company 2,220,141 Plus: Axiall debt repaid at acquisition 247,135 Seller's transaction costs paid by the Company (1) 47,458 Total fair value of consideration transferred 2,514,734 Fair value of Axiall share-based awards attributed to pre-combination service (2) 11,346 Additional settlement value of shares acquired 13,280 Purchase consideration 2,539,360 Fair value of previously held equity interest in Axiall (3) 102,300 Total fair value allocated to net assets acquired $ 2,641,660 _____________ (1) Transaction costs incurred by the seller included legal and advisory costs incurred for the benefit of Axiall's former shareholders and board of directors to evaluate the Company's initial Merger proposals, explore strategic alternatives and negotiate the purchase price. (2) The fair value of share-based awards attributable to pre-combination service includes the ratio of the pre-combination service performed to the original service period of the Axiall restricted share units and options, including related dividend equivalent rights. (3) Prior to the Merger, the Company owned 3.1 million shares in Axiall. The investment in Axiall was carried at estimated fair value with unrealized gains recorded as a component of accumulated other comprehensive loss in the consolidated balance sheet. The Company recognized a $49,080 gain for the investment in other income, net in the consolidated statements of operations upon gaining control.
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the purchase price allocation: Net Assets Acquired as of August 31, 2016 Cash $ 88,251 Accounts receivable (1) 422,274 Income tax receivable 50,980 Inventories (2) 349,205 Prepaid expenses and other current assets 55,462 Property, plant and equipment (2) 2,942,162 Customer relationships (weighted average lives of 9.8 years) (3) 670,000 Other intangible assets: Trade name (weighted average lives of 6.8 years) 50,000 Technology (weighted average lives of 5.4 years) 41,500 Supply contracts and leases (weighted average lives of 6.3 years) 27,288 Other assets 93,875 Total assets acquired 4,790,997 Accounts and notes payable 254,041 Interest payable 8,154 Income tax payable 1,607 Accrued compensation 44,186 Accrued liabilities 154,290 Deferred income taxes (4) 958,304 Tax reserve non-current 3,130 Pension and other post-retirement obligations 311,106 Other liabilities 101,325 Long-term debt 1,187,290 Total liabilities assumed 3,023,433 Total identifiable net assets acquired 1,767,564 Noncontrolling interest (68,000 ) Goodwill 942,096 Total fair value allocated to net assets acquired $ 2,641,660 ______________________________ (1) The fair value of accounts receivable acquired was $422,274 , with the gross contractual amount being $434,834 . The Company expects $12,560 to be uncollectible. (2) The Company obtained additional information related to its inventories and property, plant and equipment which led to an increase in inventories of $43,047 , a decrease in property, plant and equipment of $192,579 and a corresponding increase in goodwill of $149,532 compared to the estimated fair values included in the 2016 Form 10-K. (3) The Company obtained additional information related to its customer relationship balances which led to an increase in customer relationships of $80,000 and a corresponding decrease in goodwill compared to the estimated fair values included in the 2016 Form 10-K. (4) Decreases in the estimated fair values of identified assets acquired led to a decrease in deferred income taxes of $26,824 compared to the estimated fair values included in the 2016 Form 10-K.

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Realized Gain (Loss)	Three Months Ended September 30, Nine Months Ended September 30, 2016 2016 Proceeds from sales and maturities of securities $ 360,506 $ 662,938 Gross realized gains 52,414 53,755 Gross realized losses (13 ) (35 )

Accounts Receivable (Tables)

Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2017
Accounts Receivable, Net [Abstract]
Schedule Of Accounts Receivable	Accounts receivable consist of the following: September 30, December 31, Trade customers $ 1,111,563 $ 819,739 Affiliates 7,601 7,982 Allowance for doubtful accounts (21,961 ) (17,991 ) 1,097,203 809,730 Federal and state taxes 16,657 90,414 Other 29,119 38,599 Accounts receivable, net $ 1,142,979 $ 938,743

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following: September 30, December 31, Finished products $ 488,061 $ 500,861 Feedstock, additives and chemicals 213,144 216,877 Materials and supplies 133,630 83,362 Inventories $ 834,835 $ 801,100

Other Assets (Tables)

Other Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Amortization	Amortization expense on intangible and other assets included in cost of sales and selling, general and administrative expenses in the consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cost of sales $ 10,834 $ 10,061 $ 33,121 $ 24,452 Selling, general and administrative 26,792 9,114 81,323 13,888 Total amortization expense $ 37,626 $ 19,175 $ 114,444 $ 38,340
Changes in Carrying Amount of Goodwill	The gross carrying amounts of goodwill and the changes in the carrying amount of goodwill for the nine months ended September 30, 2017 were as follows: Olefins Segment Vinyls Segment Total Balance at December 31, 2016 $ 29,990 $ 916,563 $ 946,553 Goodwill acquired during the period — — — Measurement period adjustment — 54,605 54,605 Effects of changes in foreign exchange rates — 10,184 10,184 Balance at September 30, 2017 $ 29,990 $ 981,352 $ 1,011,342

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	Long-term debt consists of the following: September 30, 2017 December 31, 2016 Principal Unamortized Discount Net Principal Unamortized Net Revolving credit facility $ — $ — $ — $ 325,000 $ — $ 325,000 4.625% senior notes due 2021 (the "4.625% Westlake 2021 Senior Notes") 624,793 21,881 646,674 624,793 26,837 651,630 4.625% senior notes due 2021 (the "4.625% Subsidiary 2021 Senior Notes") 63,207 2,343 65,550 63,207 2,862 66,069 3.60% senior notes due 2022 250,000 (1,635 ) 248,365 250,000 (1,891 ) 248,109 4.875% senior notes due 2023 (the "4.875% Westlake 2023 Senior Notes") 433,793 11,791 445,584 433,793 13,431 447,224 4.875% senior notes due 2023 (the "4.875% Subsidiary 2023 Senior Notes") 16,207 477 16,684 16,207 540 16,747 3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes") 750,000 (10,031 ) 739,969 750,000 (10,757 ) 739,243 Loan related to tax-exempt waste disposal revenue bonds due 2027 10,889 — 10,889 10,889 — 10,889 6 ½% tax-exempt senior notes due 2029 100,000 (861 ) 99,139 100,000 (916 ) 99,084 6 ¾% tax-exempt senior notes due 2032 250,000 (605 ) 249,395 250,000 (1,883 ) 248,117 6 ½% tax-exempt senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes") 89,000 (806 ) 88,194 89,000 (839 ) 88,161 6 ½% tax-exempt senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes") 65,000 (578 ) 64,422 65,000 (602 ) 64,398 5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes") 700,000 (25,463 ) 674,537 700,000 (26,017 ) 673,983 Long-term debt, net $ 3,352,889 $ (3,487 ) $ 3,349,402 $ 3,677,889 $ 765 $ 3,678,654

Pension and Post-Retirement B37

Pension and Post-Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2017
Defined Benefit Plan [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 September 30, Nine Months Ended September 30, 2017 2016 2017 2016 U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. Service cost $ 163 $ 14 $ 72 $ 1 $ 489 $ 41 $ 81 $ 1 Interest cost 500 35 250 3 1,499 100 540 3 Amortization of net loss 15 — 31 — 45 — 94 — Net periodic benefit cost $ 678 $ 49 $ 353 $ 4 $ 2,033 $ 141 $ 715 $ 4 Components of net periodic benefit cost (income) for the Company's pension plans are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. U.S. Non-U.S. Service cost $ 1,336 $ 528 $ 315 $ 318 $ 4,007 $ 1,509 $ 315 $ 777 Expected administrative expenses — — 730 — — — 730 — Interest cost 6,198 615 2,191 622 18,594 1,754 1,553 1,763 Expected return on plan assets (9,976 ) (162 ) (3,800 ) (50 ) (29,928 ) (466 ) (5,260 ) (50 ) Amortization of net loss 297 217 338 — 892 663 978 — Net periodic benefit cost (income) $ (2,145 ) $ 1,198 $ (226 ) $ 890 $ (6,435 ) $ 3,460 $ (1,684 ) $ 2,490

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Schedule of Stockholders Equity	Changes in stockholders' equity for the nine months ended September 30, 2017 and 2016 were as follows: Common Stock Common Stock, Held in Treasury Additional Paid-in Capital Retained Earnings Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Total Balances at December 31, 2016 $ 1,347 $ (319,339 ) $ 550,641 $ 3,412,286 $ (121,306 ) $ 368,416 $ 3,892,045 Net income — — — 501,849 — 21,429 523,278 Other comprehensive income (loss), net of income taxes: Pension and other post- retirement benefits liability — — — — 1,057 (44 ) 1,013 Foreign currency translation adjustments — — — — 106,563 2,952 109,515 Other — — — — (260 ) — (260 ) Shares issued—stock- based compensation — 4,645 (2,441 ) — — — 2,204 Stock-based compensation, net of tax on stock options exercised — — 10,223 — — — 10,223 Dividends declared — — — (76,491 ) — — (76,491 ) Distributions to noncontrolling interests — — — — — (20,767 ) (20,767 ) Issuance of Westlake Chemical Partners LP common units — — — — — 110,739 110,739 Balances at September 30, 2017 $ 1,347 $ (314,694 ) $ 558,423 $ 3,837,644 $ (13,946 ) $ 482,725 $ 4,551,499 Common Stock Common Stock, Held in Treasury Additional Paid-in Capital Retained Earnings Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Total Balances at December 31, 2015 $ 1,347 $ (258,312 ) $ 542,148 $ 3,109,987 $ (129,292 ) $ 296,053 $ 3,561,931 Net income — — — 299,914 — 14,656 314,570 Other comprehensive income (loss), net of income taxes Pension and other post- retirement benefits liability — — — — 409 — 409 Foreign currency translation adjustments — — — — 15,758 — 15,758 Net unrealized holding gains on investments — — — — 4,999 — 4,999 Common stock repurchased — (66,725 ) — — — — (66,725 ) Shares issued—stock- based compensation — 5,057 (3,407 ) — — — 1,650 Stock-based compensation, net of tax on stock options exercised — — 7,778 — — — 7,778 Dividends declared — — — (71,933 ) — — (71,933 ) Distributions to noncontrolling interests — — — — — (12,300 ) (12,300 ) Noncontrolling interest in acquired business — — — — — 68,000 68,000 Balances at September 30, 2016 $ 1,347 $ (319,980 ) $ 546,519 $ 3,337,968 $ (108,126 ) $ 366,409 $ 3,824,137
Schedule of Accumulated Other Comprehensive Income (Loss)	Changes in accumulated other comprehensive income (loss) by component for the nine months ended September 30, 2017 and 2016 were as follows: Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Net Unrealized Holding Gains (Losses) on Investments, Net of Tax Total Balances at December 31, 2016 $ 28,945 $ (150,202 ) $ (49 ) $ (121,306 ) Other comprehensive income (loss) before reclassifications — 106,563 (260 ) 106,303 Amounts reclassified from accumulated other comprehensive loss 1,057 — — 1,057 Net other comprehensive income (loss) for the period 1,057 106,563 (260 ) 107,360 Balances at September 30, 2017 $ 30,002 $ (43,639 ) $ (309 ) $ (13,946 ) Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Net Unrealized Holding Gains (Losses) on Investments, Net of Tax Total Balances at December 31, 2015 $ (8,607 ) $ (115,690 ) $ (4,995 ) $ (129,292 ) Other comprehensive income (loss) before reclassifications (252 ) 15,758 57,550 73,056 Amounts reclassified from accumulated other comprehensive loss (income) 661 — (52,551 ) (51,890 ) Net other comprehensive income for the period 409 15,758 4,999 21,166 Balances at September 30, 2016 $ (8,198 ) $ (99,932 ) $ 4 $ (108,126 )
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 and nine months ended September 30, 2017 and 2016 : Details about Accumulated Other Comprehensive Income (Loss) Components Location of Reclassification (Income (Expense)) in Consolidated Statements of Operations Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Amortization of pension and other post-retirement items Net loss (1) $ (529 ) $ (369 ) $ (1,600 ) $ (1,072 ) Benefit from income taxes 193 141 543 411 (336 ) (228 ) (1,057 ) (661 ) Net unrealized gains on available-for-sale investments Realized gain on available-for-sale investments Other income, net — 52,401 — 53,720 Provision for income taxes — (696 ) — (1,169 ) — 51,705 — 52,551 Total reclassifications for the period $ (336 ) $ 51,477 $ (1,057 ) $ 51,890 _____________ (1) These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost. For additional information, please read Note 13 (Employee Benefits) to the consolidated financial statements included in the 2016 Form 10-K.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Impact of Derivatives Net In Consolidated Balance Sheet [Table Text Block]	September 30, 2017 Net Presentation Gross Presentation Net Assets (Liabilities) Presented in the Consolidated Balance Sheets Risk management assets—Commodity forward contracts Risk management liabilities—Commodity forward contracts Accounts receivable, net Derivative positions subject to enforceable master netting arrangements $ 793 $ 2,778 $ (1,985 ) Derivative positions not subject to enforceable master netting arrangements 4,557 4,557 — 5,350 7,335 (1,985 ) Deferred charges and other assets, net Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting 4,336 4,336 — 4,336 4,336 — Accrued liabilities Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting (704 ) — (704 ) (704 ) — (704 ) Other liabilities Derivative positions subject to enforceable master netting (1,410 ) 745 (2,155 ) Derivative positions not subject to enforceable master netting (2,774 ) — (2,774 ) (4,184 ) 745 (4,929 ) Risk management assets (liabilities)—Commodity forward contracts $ 12,416 $ (7,618 ) December 31, 2016 Net Presentation Gross Presentation Net Assets (Liabilities) Presented in the Consolidated Balance Sheets Risk management assets—Commodity forward contracts Risk management liabilities—Commodity forward contracts Accounts receivable, net Derivative positions subject to enforceable master netting $ 1,498 $ 1,636 $ (138 ) Derivative positions not subject to enforceable master netting 6,091 6,091 — 7,589 7,727 (138 ) Deferred charges and other assets, net Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting 5,249 5,249 — 5,249 5,249 — Accrued liabilities Derivative positions subject to enforceable master netting — — — Derivative positions not subject to enforceable master netting (1,349 ) — (1,349 ) (1,349 ) — (1,349 ) Other liabilities Derivative positions subject to enforceable master netting (436 ) 2,010 (2,446 ) Derivative positions not subject to enforceable master netting (3,288 ) — (3,288 ) (3,724 ) 2,010 (5,734 ) Risk management assets (liabilities)—Commodity forward contracts $ 14,986 $ (7,221 )
Impact of Derivative Instruments Not Designated as Fair Value Hedges	The impacts 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 Hedging Instruments Location of Gain (Loss) Recognized in Income on Derivative Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Commodity forward contracts Cost of sales $ 6,846 $ (7,840 ) $ (2,756 ) $ 7,784

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
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: September 30, 2017 Level 1 Level 2 Total Derivative instruments Risk management assets—Commodity forward contracts $ 233 $ 12,183 $ 12,416 Risk management liabilities—Commodity forward contracts (6,183 ) (1,435 ) (7,618 ) December 31, 2016 Level 1 Level 2 Total Derivative instruments Risk management assets—Commodity forward contracts $ 878 $ 14,108 $ 14,986 Risk management liabilities—Commodity forward contracts (6,854 ) (367 ) (7,221 )
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 fair value of the Company's long-term debt instruments is determined using a market approach, based upon quotes from financial reporting services. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy. September 30, 2017 December 31, 2016 Carrying Value Fair Value Carrying Value Fair Value Revolving credit facility $ — $ — $ 325,000 $ 325,000 4.625% Westlake 2021 Senior Notes 646,674 646,486 651,630 650,847 4.625% Subsidiary 2021 Senior Notes 65,550 62,983 66,069 65,775 3.60% senior notes due 2022 248,365 255,733 248,109 251,725 4.875% Westlake 2023 Senior Notes 445,584 452,004 447,224 451,301 4.875% Subsidiary 2023 Senior Notes 16,684 16,842 16,747 16,501 3.60% 2026 Senior Notes 739,969 749,570 739,243 722,055 Loan related to tax-exempt waste disposal revenue bonds due 2027 10,889 10,889 10,889 10,889 6 ½% tax-exempt senior notes due 2029 99,139 113,789 99,084 112,433 6 ¾% tax-exempt senior notes due 2032 249,395 251,250 248,117 258,818 6 ½% 2035 GO Zone Senior Notes 88,194 100,936 88,161 100,323 6 ½% 2035 IKE Zone Senior Notes 64,422 73,908 64,398 73,270 5.0% 2046 Senior Notes 674,537 760,739 673,983 691,712

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Schedule Of Net Income Attributable To Common Stockholders	Diluted earnings per share include the effect of certain stock options. Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net income attributable to Westlake Chemical Corporation $ 210,832 $ 65,662 $ 501,849 $ 299,914 Less: Net income attributable to participating securities (1,117 ) (294 ) (2,630 ) (1,347 ) Net income attributable to common shareholders $ 209,715 $ 65,368 $ 499,219 $ 298,567
Reconciliation Of Denominator For Basic And Diluted Earnings Per Share	The following table reconciles the denominator for the basic and diluted earnings per share computations shown in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Weighted average common shares—basic 129,069,186 128,793,661 129,033,597 129,519,577 Plus incremental shares from: Assumed exercise of options 819,782 586,295 756,368 584,320 Weighted average common shares—diluted 129,888,968 129,379,956 129,789,965 130,103,897 Earnings per common share attributable to Westlake Chemical Corporation: Basic $ 1.62 $ 0.51 $ 3.87 $ 2.31 Diluted $ 1.61 $ 0.51 $ 3.85 $ 2.29

Supplemental Information (Table

Supplemental Information (Tables)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Other Income	Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Interest income $ 644 $ 537 $ 1,578 $ 6,900 Dividend income 127 574 250 1,499 Acquisition-related financing costs — (11,420 ) — (12,220 ) Foreign exchange currency loss, net (3,197 ) (1,281 ) (9,483 ) (2,435 ) Gain realized on previously held shares of Axiall common stock — 49,080 — 49,080 Gains from sales of securities, net — 3,321 — 4,640 Income from non-consolidated subsidiaries 3,855 1,475 11,066 7,213 Other 629 (1,021 ) 3,180 (2,586 ) Other income, net $ 2,058 $ 41,265 $ 6,591 $ 52,091

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Reporting Information	Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Net external sales Olefins Polyethylene $ 377,269 $ 380,810 $ 1,121,603 $ 1,098,500 Styrene, feedstock and other 124,974 116,555 412,869 324,369 Total Olefins 502,243 497,365 1,534,472 1,422,869 Vinyls PVC, caustic soda and other 1,252,963 599,276 3,541,409 1,492,650 Building products 353,683 182,387 954,785 424,757 Total Vinyls 1,606,646 781,663 4,496,194 1,917,407 $ 2,108,889 $ 1,279,028 $ 6,030,666 $ 3,340,276 Intersegment sales Olefins $ 106,722 $ 30,614 $ 290,658 $ 85,856 Vinyls 260 2,130 871 2,719 $ 106,982 $ 32,744 $ 291,529 $ 88,575 Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income (loss) from operations Olefins $ 165,438 $ 118,475 $ 488,532 $ 408,274 Vinyls 216,515 22,235 431,276 136,559 Corporate and other (16,206 ) (94,147 ) (51,647 ) (116,056 ) $ 365,747 $ 46,563 $ 868,161 $ 428,777 Depreciation and amortization Olefins $ 35,029 $ 36,649 $ 111,244 $ 95,582 Vinyls 117,490 56,136 331,585 128,691 Corporate and other 1,115 1,444 5,704 2,920 $ 153,634 $ 94,229 $ 448,533 $ 227,193 Other income (expense), net Olefins $ (184 ) $ 1,101 $ 1,555 $ 3,706 Vinyls (970 ) (1,226 ) 1,087 1,722 Corporate and other 3,212 41,390 3,949 46,663 $ 2,058 $ 41,265 $ 6,591 $ 52,091 Provision for (benefit from) income taxes Olefins $ 58,218 $ 31,956 $ 152,482 $ 136,429 Vinyls 60,784 (3,912 ) 114,979 29,655 Corporate and other (10,383 ) (34,596 ) (34,771 ) (36,752 ) $ 108,619 $ (6,552 ) $ 232,690 $ 129,332 Capital expenditures Olefins $ 20,960 $ 96,469 $ 70,043 $ 285,359 Vinyls 107,515 83,523 329,968 180,392 Corporate and other 4,894 178 14,260 1,579 $ 133,369 $ 180,170 $ 414,271 $ 467,330
Reconciliation Of Total Segment Income From Operations To Consolidated Income Before Income Taxes	A reconciliation of total segment income from operations to consolidated income before income taxes is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Income from operations $ 365,747 $ 46,563 $ 868,161 $ 428,777 Interest expense (40,036 ) (24,366 ) (118,784 ) (36,966 ) Other income (expense), net 2,058 41,265 6,591 52,091 Income before income taxes $ 327,769 $ 63,462 $ 755,968 $ 443,902
Total Assets	September 30, December 31, Total assets Olefins $ 2,015,888 $ 2,092,617 Vinyls 8,695,509 8,287,204 Corporate and other 532,728 510,432 $ 11,244,125 $ 10,890,253

Guarantor Disclosures (Tables)

Guarantor Disclosures (Tables)	9 Months Ended
	Sep. 30, 2017
Guarantees [Abstract]
Condensed Consolidating Financial Information Balance Sheet	Condensed Consolidating Financial Information as of September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Balance Sheet Current assets Cash and cash equivalents $ 334,111 $ 33,089 $ 311,033 $ — $ 678,233 Accounts receivable, net 3,060,591 4,048,824 432,238 (6,398,674 ) 1,142,979 Inventories — 631,322 203,513 — 834,835 Prepaid expenses and other current assets 16,616 31,785 22,365 (35,906 ) 34,860 Restricted cash — 1,275 7,351 — 8,626 Total current assets 3,411,318 4,746,295 976,500 (6,434,580 ) 2,699,533 Property, plant and equipment, net — 4,330,104 2,013,533 — 6,343,637 Other assets, net Goodwill — 854,896 156,446 — 1,011,342 Customer relationships, net — 493,960 141,924 — 635,884 Other intangible assets, net — 92,155 74,011 — 166,166 Deferred charges and other assets, net 9,890,164 551,732 1,372,070 (11,426,403 ) 387,563 Total other assets, net 9,890,164 1,992,743 1,744,451 (11,426,403 ) 2,200,955 Total assets $ 13,301,482 $ 11,069,142 $ 4,734,484 $ (17,860,983 ) $ 11,244,125 Current liabilities Accounts payable $ 5,821,323 $ 830,824 $ 128,673 $ (6,220,016 ) $ 560,804 Accrued liabilities 155,106 436,816 232,114 (214,564 ) 609,472 Total current liabilities 5,976,429 1,267,640 360,787 (6,434,580 ) 1,170,276 Long-term debt, net 3,256,280 4,334,142 223,578 (4,464,598 ) 3,349,402 Deferred income taxes — 1,577,209 106,587 (22,882 ) 1,660,914 Pension and other liabilities — 364,011 148,023 — 512,034 Total liabilities 9,232,709 7,543,002 838,975 (10,922,060 ) 6,692,626 Total Westlake Chemical Corporation stockholders' equity 4,068,773 3,526,140 3,412,784 (6,938,923 ) 4,068,774 Noncontrolling interests — — 482,725 — 482,725 Total equity 4,068,773 3,526,140 3,895,509 (6,938,923 ) 4,551,499 Total liabilities and equity $ 13,301,482 $ 11,069,142 $ 4,734,484 $ (17,860,983 ) $ 11,244,125 Condensed Consolidating Financial Information as of December 31, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non-Guarantor Subsidiaries Eliminations Consolidated Balance Sheet Current assets Cash and cash equivalents $ 146,990 $ 53,006 $ 259,457 $ — $ 459,453 Accounts receivable, net 2,117,540 3,329,871 323,931 (4,832,599 ) 938,743 Inventories — 597,819 203,281 — 801,100 Prepaid expenses and other current assets 30,748 41,755 12,494 (36,504 ) 48,493 Restricted cash — — 160,527 — 160,527 Total current assets 2,295,278 4,022,451 959,690 (4,869,103 ) 2,408,316 Property, plant and equipment, net — 4,475,943 1,944,119 — 6,420,062 Other assets, net Goodwill — 791,706 154,847 — 946,553 Customer relationships, net — 468,645 142,970 — 611,615 Other intangible assets, net — 130,243 71,177 (25,581 ) 175,839 Deferred charges and other assets, net 9,170,042 874,003 1,115,877 (10,832,054 ) 327,868 Total other assets, net 9,170,042 2,264,597 1,484,871 (10,857,635 ) 2,061,875 Total assets $ 11,465,320 $ 10,762,991 $ 4,388,680 $ (15,726,738 ) $ 10,890,253 Current liabilities Accounts payable $ 4,330,375 $ 748,364 $ 225,300 $ (4,807,780 ) $ 496,259 Accrued liabilities 26,367 389,216 183,223 (61,323 ) 537,483 Term loan — — 149,341 — 149,341 Total current liabilities 4,356,742 1,137,580 557,864 (4,869,103 ) 1,183,083 Long-term debt, net 3,584,949 4,090,775 — (3,997,070 ) 3,678,654 Deferred income taxes — 1,581,260 91,809 (22,494 ) 1,650,575 Pension and other liabilities — 360,622 125,274 — 485,896 Total liabilities 7,941,691 7,170,237 774,947 (8,888,667 ) 6,998,208 Total Westlake Chemical Corporation stockholders' equity 3,523,629 3,592,754 3,245,317 (6,838,071 ) 3,523,629 Noncontrolling interests — — 368,416 — 368,416 Total equity 3,523,629 3,592,754 3,613,733 (6,838,071 ) 3,892,045 Total liabilities and equity $ 11,465,320 $ 10,762,991 $ 4,388,680 $ (15,726,738 ) $ 10,890,253
Condensed Consolidating Financial Information Statement Of Operations	Condensed Consolidating Financial Information for the Three Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 1,704,086 $ 837,536 $ (432,733 ) $ 2,108,889 Cost of sales — 1,371,813 665,124 (426,100 ) 1,610,837 Gross profit — 332,273 172,412 (6,633 ) 498,052 Selling, general and administrative expenses 1,509 93,149 37,617 (6,633 ) 125,642 Transaction and integration-related costs — 6,387 276 — 6,663 Income (loss) from operations (1,509 ) 232,737 134,519 — 365,747 Other income (expense) Interest expense (38,811 ) (44,381 ) (1,635 ) 44,791 (40,036 ) Other income, net 37,563 2,517 6,769 (44,791 ) 2,058 Income (loss) before income taxes (2,757 ) 190,873 139,653 — 327,769 Provision for (benefit from) income taxes (599 ) 92,597 16,621 — 108,619 Equity in net income of subsidiaries 212,989 — — (212,989 ) — Net income 210,831 98,276 123,032 (212,989 ) 219,150 Net income attributable to noncontrolling interests — — 8,318 — 8,318 Net income attributable to Westlake Chemical Corporation $ 210,831 $ 98,276 $ 114,714 $ (212,989 ) $ 210,832 Comprehensive income attributable to Westlake Chemical Corporation $ 254,400 $ 98,455 $ 158,160 $ (256,615 ) $ 254,400 Condensed Consolidating Financial Information for the Three Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 984,937 $ 611,983 $ (317,892 ) $ 1,279,028 Cost of sales — 892,198 497,460 (312,763 ) 1,076,895 Gross profit — 92,739 114,523 (5,129 ) 202,133 Selling, general and administrative expenses 2,092 47,952 27,814 (5,129 ) 72,729 Transactions and integration-related costs — 82,687 154 — 82,841 Income (loss) from operations (2,092 ) (37,900 ) 86,555 — 46,563 Other income (expense) Interest expense (22,130 ) (22,207 ) (908 ) 20,879 (24,366 ) Other income (expense), net 35,405 (15,189 ) 41,928 (20,879 ) 41,265 Income (loss) before income taxes 11,183 (75,296 ) 127,575 — 63,462 Provision for (benefit from) income taxes (2,088 ) (11,080 ) 6,616 — (6,552 ) Equity in net income of subsidiaries 52,391 — — (52,391 ) — Net income 65,662 (64,216 ) 120,959 (52,391 ) 70,014 Net income attributable to noncontrolling interests — — 4,352 — 4,352 Net income attributable to Westlake Chemical Corporation $ 65,662 $ (64,216 ) $ 116,607 $ (52,391 ) $ 65,662 Comprehensive income attributable to Westlake Chemical Corporation $ 39,636 $ (64,113 ) $ 104,129 $ (40,015 ) $ 39,637 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 4,880,682 $ 2,377,862 $ (1,227,878 ) $ 6,030,666 Cost of sales — 4,077,633 1,889,571 (1,207,567 ) 4,759,637 Gross profit — 803,049 488,291 (20,311 ) 1,271,029 Selling, general and administrative expenses 2,429 281,412 116,389 (20,311 ) 379,919 Transaction and integration-related costs — 22,611 338 — 22,949 Income (loss) from operations (2,429 ) 499,026 371,564 — 868,161 Other income (expense) Interest expense (115,156 ) (133,048 ) (5,623 ) 135,043 (118,784 ) Other income, net 112,002 2,944 26,688 (135,043 ) 6,591 Income (loss) before income taxes (5,583 ) 368,922 392,629 — 755,968 Provision for (benefit from) income taxes (1,451 ) 198,054 36,087 — 232,690 Equity in net income of subsidiaries 505,981 — — (505,981 ) — Net income 501,849 170,868 356,542 (505,981 ) 523,278 Net income attributable to noncontrolling interests — — 21,429 — 21,429 Net income attributable to Westlake Chemical Corporation $ 501,849 $ 170,868 $ 335,113 $ (505,981 ) $ 501,849 Comprehensive income attributable to Westlake Chemical Corporation $ 613,350 $ 171,413 $ 233,030 $ (404,443 ) $ 613,350 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Operations Net sales $ — $ 2,567,232 $ 1,734,611 $ (961,567 ) $ 3,340,276 Cost of sales — 2,233,395 1,353,764 (945,967 ) 2,641,192 Gross profit — 333,837 380,847 (15,600 ) 699,084 Selling, general and administrative expenses 3,648 121,261 70,448 (15,600 ) 179,757 Transaction and integration-related costs — 90,396 154 — 90,550 Income (loss) from operations (3,648 ) 122,180 310,245 — 428,777 Other income (expense) Interest expense (43,228 ) (39,693 ) (1,054 ) 47,009 (36,966 ) Other income (expense), net 40,807 (22,291 ) 80,584 (47,009 ) 52,091 Income (loss) before income taxes (6,069 ) 60,196 389,775 — 443,902 Provision for (benefit from) income taxes (8,268 ) 106,792 30,808 — 129,332 Equity in net income of subsidiaries 297,715 — — (297,715 ) — Net income 299,914 (46,596 ) 358,967 (297,715 ) 314,570 Net income attributable to noncontrolling interests — — 14,656 — 14,656 Net income attributable to Westlake Chemical Corporation $ 299,914 $ (46,596 ) $ 344,311 $ (297,715 ) $ 299,914 Comprehensive income attributable to Westlake Chemical Corporation $ 321,079 $ (46,187 ) $ 364,402 $ (318,214 ) $ 321,080
Condensed Consolidating Financial Information Statement Of Cash Flows	Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2017 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Cash Flows Cash flows from operating activities Net income $ 501,849 $ 170,868 $ 356,542 $ (505,981 ) $ 523,278 Adjustments to reconcile net income to net cash provided by (used for) operating activities Depreciation and amortization — 294,227 154,306 — 448,533 Deferred income taxes (217 ) 20,299 3,212 — 23,294 Net changes in working capital and other (532,120 ) (129,330 ) 123,028 505,981 (32,441 ) Net cash provided by (used for) operating activities (30,488 ) 356,064 637,088 — 962,664 Cash flows from investing activities Additions to property, plant and equipment — (294,138 ) (120,133 ) — (414,271 ) Additions to cost method investment — (47,000 ) — — (47,000 ) Proceeds from disposition of assets — 25 146 — 171 Proceeds from involuntary conversion of assets — — 1,672 — 1,672 Receivable under the investment management agreement — — (119,000 ) 119,000 — Settlements of derivative instruments — (7 ) — — (7 ) Net cash used for investing activities — (341,120 ) (237,315 ) 119,000 (459,435 ) Cash flows from financing activities Intercompany financing 498,272 (313,276 ) (184,996 ) — — Receivable under the investment management agreement 119,000 — — (119,000 ) — Debt issuance costs (376 ) — — — (376 ) Dividends paid (76,491 ) — — — (76,491 ) Distributions to noncontrolling interests — 279,203 (299,970 ) — (20,767 ) Net proceeds from issuance of Westlake Chemical Partners LP common units — — 110,739 — 110,739 Proceeds from issuance of notes payable — — 5,946 — 5,946 Proceeds from drawdown of revolver 225,000 — — — 225,000 Restricted cash associated with term loan — — 154,000 — 154,000 Repayment of term loan — — (150,000 ) — (150,000 ) Repayment of notes payable — (788 ) (5,907 ) — (6,695 ) Repayment of revolver (550,000 ) — — — (550,000 ) Other 2,204 — — — 2,204 Net cash provided by (used for) financing activities 217,609 (34,861 ) (370,188 ) (119,000 ) (306,440 ) Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Effect of exchange rate changes on cash and cash equivalents — — 21,991 — 21,991 Net increase (decrease) in cash and cash equivalents 187,121 (19,917 ) 51,576 — 218,780 Cash and cash equivalents at beginning of period 146,990 53,006 259,457 — 459,453 Cash and cash equivalents at end of period $ 334,111 $ 33,089 $ 311,033 $ — $ 678,233 Condensed Consolidating Financial Information for the Nine Months Ended September 30, 2016 Westlake Chemical Corporation 100% Owned Guarantor Subsidiaries Non- Guarantor Subsidiaries Eliminations Consolidated Statement of Cash Flows Cash flows from operating activities Net income $ 299,914 $ (46,596 ) $ 358,967 $ (297,715 ) $ 314,570 Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities Depreciation and amortization — 118,645 108,548 — 227,193 Deferred income taxes (5,178 ) 100,908 10,180 — 105,910 Net changes in working capital and other (313,676 ) (39,859 ) (47,693 ) 297,715 (103,513 ) Net cash provided by (used for) operating activities (18,940 ) 133,098 430,002 — 544,160 Cash flows from investing activities Acquisition of business, net of cash acquired — (2,437,829 ) — — (2,437,829 ) Additions to property, plant and equipment — (162,288 ) (305,042 ) — (467,330 ) Additions to cost method investment — (4,000 ) — — (4,000 ) Proceeds from disposition of assets — 48 165 — 213 Proceeds from sales and maturities of securities 658,338 — 4,600 — 662,938 Purchase of securities (138,422 ) — — — (138,422 ) Settlements of derivative instruments — (4,655 ) — — (4,655 ) Net cash provided by (used for) investing activities 519,916 (2,608,724 ) (300,277 ) — (2,389,085 ) Cash flows from financing activities Intercompany financing (2,242,604 ) 2,289,200 (46,596 ) — — Debt issuance costs (33,617 ) — (1,590 ) — (35,207 ) Dividends paid (71,933 ) — — — (71,933 ) Distributions to noncontrolling interests — 202,210 (214,510 ) — (12,300 ) Proceeds from debt issuance 1,428,512 — — — 1,428,512 Proceeds from issuance of notes payable — — 5,597 — 5,597 Proceeds from term loan and drawdown of revolver 450,000 — 150,000 — 600,000 Restricted cash associated with term loan — — (154,000 ) — (154,000 ) Repayment of notes payable — — (10,602 ) — (10,602 ) Repayment of revolver (125,000 ) — — — (125,000 ) Repurchase of common stock for treasury (67,406 ) — — — (67,406 ) Other 2,840 — — — 2,840 Net cash provided by (used for) financing activities (659,208 ) 2,491,410 (271,701 ) — 1,560,501 Effect of exchange rate changes on cash and cash equivalents — — 2,418 — 2,418 Net increase (decrease) in cash and cash equivalents (158,232 ) 15,784 (139,558 ) — (282,006 ) Cash and cash equivalents at beginning of period 303,131 6,818 352,576 — 662,525 Cash and cash equivalents at end of period $ 144,899 $ 22,602 $ 213,018 $ — $ 380,519

Acquisition (Narrative) (Detail

Acquisition (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Aug. 31, 2016	Aug. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Transaction and integration-related costs			$ 6,663	$ 82,841	$ 22,949	$ 90,550
Transaction costs				$ 43,895		43,895
Share-based awards, retention & severance						$ 46,655
Axiall Corporation [Member]
Business Acquisition [Line Items]
Equity interest in acquiree held prior to combination, shares		3.1
Offer per share	$ 33
Purchase consideration	$ 2,539,360

Acquisition (Pro Forma) (Detail

Acquisition (Pro Forma) (Details) - USD ($) $ / shares in Units, $ in Thousands	8 Months Ended	9 Months Ended
	Aug. 30, 2016	Sep. 30, 2016
Business Acquisition, Pro Forma Information [Line Items]
Net sales		$ 5,345,365
Net income		277,567
Net income attributable to noncontrolling interest		16,404
Net income attributable to Westlake Chemical Corporation		$ 261,163
Basic (in dollars per share)		$ 2.01
Diluted (in dollars per share)		$ 2
Axiall Corporation [Member]
Business Acquisition, Pro Forma Information [Line Items]
Divestitures	$ 26,666
Restructuring costs	22,881
Legal and settlement claims, net	$ 23,376

Acquisition (Allocation of Purc

Acquisition (Allocation of Purchase Consideration) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	Aug. 31, 2016	Aug. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill			$ 1,011,342	$ 946,553
Axiall Corporation [Member]
Business Acquisition [Line Items]
Goodwill	$ 942,096
Offer per share (in dollars per share)	$ 33
Multiplied by number of shares outstanding at acquisition	67,277
Fair value of Axiall shares outstanding purchased by the Company	$ 2,220,141
Axiall debt repaid at acquisition	247,135
Seller's transaction costs paid by the Company	47,458
Total fair value of consideration transferred	2,514,734
Fair value of Axiall share-based awards attributed to pre-combination service	11,346
Additional settlement value of shares acquired	13,280
Purchase consideration	2,539,360
Fair value of previously held equity interest in Axiall	102,300
Total fair value allocated to net assets acquired	2,641,660
Equity interest in acquiree held prior to combination, shares		3,100
Step acquisition, equity interest in acquiree, remeasurement gain (loss), net	$ 49,080

Acquisition (Purchase Price All

Acquisition (Purchase Price Allocation) (Details) - USD ($) $ in Thousands	Aug. 31, 2016	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill		$ 1,011,342	$ 946,553
Goodwill, Purchase Accounting Adjustments		$ 54,605
Axiall Customer Relationships [Member]
Business Acquisition [Line Items]
Weighted average useful life	9 years 9 months 18 days
Axiall Trade Name [Member]
Business Acquisition [Line Items]
Weighted average useful life	6 years 9 months 18 days
Axiall Technology [Member]
Business Acquisition [Line Items]
Weighted average useful life	5 years 4 months 24 days
Axiall Supply Contracts and Leases [Member]
Business Acquisition [Line Items]
Weighted average useful life	6 years 3 months 18 days
Axiall Corporation [Member]
Business Acquisition [Line Items]
Cash	$ 88,251
Accounts Receivable (1)	422,274
Income tax receivable	50,980
Inventories (2)	349,205
Prepaid expenses and other current assets	55,462
Property, plant and equipment (2)	2,942,162
Other assets	93,875
Total assets acquired	4,790,997
Accounts and notes payable	254,041
Interest payable	8,154
Income tax payable	1,607
Accrued compensation	44,186
Accrued liabilities	154,290
Deferred income taxes (4)	958,304
Tax reserve non-current	3,130
Pension and other post-retirement obligations	311,106
Other liabilities	101,325
Long-term debt	1,187,290
Total liabilities assumed	3,023,433
Total identifiable net assets acquired	1,767,564
Noncontrolling interest	(68,000)
Goodwill	942,096
Total fair value allocated to net assets acquired	2,641,660
Business Combination, Acquired Receivables, Gross Contractual Amount	434,834
Business Combination, Acquired Receivables, Estimated Uncollectible	12,560
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory	43,047
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment	(192,579)
Goodwill, Purchase Accounting Adjustments	149,532
Axiall Corporation [Member] | Axiall Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-lived intangibles	670,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles	80,000
Axiall Corporation [Member] | Axiall Trade Name [Member]
Business Acquisition [Line Items]
Finite-lived intangibles	50,000
Axiall Corporation [Member] | Axiall Technology [Member]
Business Acquisition [Line Items]
Finite-lived intangibles	41,500
Axiall Corporation [Member] | Axiall Supply Contracts and Leases [Member]
Business Acquisition [Line Items]
Finite-lived intangibles	27,288
Deferred Income Tax Change [Member]
Business Acquisition [Line Items]
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustments Related to Previous Period	$ (26,824)

Financial Instruments (Restrict

Financial Instruments (Restricted Cash Equivalents) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Restricted cash	$ 31,682	$ 186,216
Current Restricted Cash	8,626	160,527
Noncurrent Restricted Cash	$ 23,056	$ 25,689

Financial Instruments (Availabl

Financial Instruments (Available-for-Sale Marketable Securities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Available-for-sale Securities	$ 0		$ 0		$ 0
Proceeds from Sale and Maturity of Available-for-sale Securities	$ 0	$ 360,506	$ 0	$ 662,938
Available-for-sale Securities, Gross Realized Gains		52,414		53,755
Available-for-sale Securities, Gross Realized Losses		$ (13)		$ (35)

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accounts Receivable, Net [Abstract]
Trade customers	$ 1,111,563	$ 819,739
Affiliates	7,601	7,982
Allowance for doubtful accounts	(21,961)	(17,991)
Accounts receivable from trade customers, net	1,097,203	809,730
Federal and state taxes	16,657	90,414
Other	29,119	38,599
Accounts receivable, net	$ 1,142,979	$ 938,743

Inventories (Inventories) (Deta

Inventories (Inventories) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Finished products	$ 488,061	$ 500,861
Feedstock, additives and chemicals	213,144	216,877
Materials and supplies	133,630	83,362
Inventories	$ 834,835	$ 801,100

Property, Plant and Equipment (

Property, Plant and Equipment (Property, Plant and Equipment) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, plant and equipment, net	$ 6,343,637		$ 6,343,637		$ 6,420,062
Depreciation expense on property, plant and equipment	$ 116,160	$ 75,143	$ 334,545	$ 189,114

Other Assets (Amortization Expe

Other Assets (Amortization Expense) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cost of Sales [Member]
Other Assets [Line Items]
Amortization of Other Assets	$ 10,834	$ 10,061	$ 33,121	$ 24,452
Selling, General and Administrative Expenses [Member]
Other Assets [Line Items]
Amortization of Other Assets	26,792	9,114	81,323	13,888
Other Assets [Member]
Other Assets [Line Items]
Amortization of Other Assets	$ 37,626	$ 19,175	$ 114,444	$ 38,340

Other Assets (Changes in Goodwi

Other Assets (Changes in Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 946,553
Goodwill acquired during the period	0
Goodwill, Purchase Accounting Adjustments	54,605
Effects of changes in foreign exchange rates	10,184
Ending Balance	1,011,342
Olefins [Member]
Goodwill [Roll Forward]
Beginning Balance	29,990
Goodwill acquired during the period	0
Goodwill, Purchase Accounting Adjustments	0
Effects of changes in foreign exchange rates	0
Ending Balance	29,990
Vinyls [Member]
Goodwill [Roll Forward]
Beginning Balance	916,563
Goodwill acquired during the period	0
Goodwill, Purchase Accounting Adjustments	54,605
Effects of changes in foreign exchange rates	10,184
Ending Balance	$ 981,352

Term Loan (Narrative) (Details)

Term Loan (Narrative) (Details) - Line of Credit [Member] - Term Loan Facility Maturing March 31, 2017 [Member] $ in Thousands	Aug. 10, 2016USD ($)
Note Payable to Bank [Line Items]
Note Payable to Bank Borrowing	$ 150,000
LIBOR [Member]
Note Payable to Bank [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%

Long-Term Debt (Schedule of Lon

Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Mar. 27, 2017	Dec. 31, 2016	Sep. 30, 2016
Debt Instrument [Line Items]
Principal Amount	$ 3,352,889		$ 3,677,889
Unamortized Premium, Discount and Debt Issuance Costs,	(3,487)		765
Net, Long-term Debt	3,349,402		3,678,654
Line of Credit [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Principal Amount	0		325,000
Unamortized Premium, Discount and Debt Issuance Costs,	0		0
Net, Long-term Debt	$ 0		325,000
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,021
Stated interest rate (percent)	4.625%			4.625%
Principal Amount	$ 624,793		624,793	$ 624,793
Unamortized Premium, Discount and Debt Issuance Costs,	21,881		26,837
Net, Long-term Debt	$ 646,674		651,630
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,021
Stated interest rate (percent)	4.625%	4.625%		4.625%
Principal Amount	$ 63,207	$ 63,207	63,207	$ 688,000
Unamortized Premium, Discount and Debt Issuance Costs,	2,343		2,862
Net, Long-term Debt	$ 65,550		66,069
Senior Notes [Member] | 3.60% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,022
Stated interest rate (percent)	3.60%
Principal Amount	$ 250,000		250,000
Unamortized Premium, Discount and Debt Issuance Costs,	(1,635)		(1,891)
Net, Long-term Debt	$ 248,365		248,109
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,023
Stated interest rate (percent)	4.875%			4.875%
Principal Amount	$ 433,793		433,793	$ 433,793
Unamortized Premium, Discount and Debt Issuance Costs,	11,791		13,431
Net, Long-term Debt	$ 445,584		447,224
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,023
Stated interest rate (percent)	4.875%	4.875%		4.875%
Principal Amount	$ 16,207	$ 16,207	16,207	$ 450,000
Unamortized Premium, Discount and Debt Issuance Costs,	477		540
Net, Long-term Debt	$ 16,684		16,747
Senior Notes [Member] | 3.6% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,026
Stated interest rate (percent)	3.60%
Principal Amount	$ 750,000		750,000
Unamortized Premium, Discount and Debt Issuance Costs,	(10,031)		(10,757)
Net, Long-term Debt	$ 739,969		739,243
Senior Notes [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,027
Principal Amount	$ 10,889		10,889
Unamortized Premium, Discount and Debt Issuance Costs,	0		0
Net, Long-term Debt	$ 10,889		10,889
Senior Notes [Member] | 6 1/2% Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,029
Stated interest rate (percent)	6.50%
Principal Amount	$ 100,000		100,000
Unamortized Premium, Discount and Debt Issuance Costs,	(861)		(916)
Net, Long-term Debt	$ 99,139		99,084
Senior Notes [Member] | 6 3/4% Senior Notes Due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,032
Stated interest rate (percent)	6.75%
Principal Amount	$ 250,000		250,000
Unamortized Premium, Discount and Debt Issuance Costs,	(605)		(1,883)
Net, Long-term Debt	$ 249,395		248,117
Senior Notes [Member] | 2035 GO Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,035
Stated interest rate (percent)	6.50%
Principal Amount	$ 89,000		89,000
Unamortized Premium, Discount and Debt Issuance Costs,	(806)		(839)
Net, Long-term Debt	$ 88,194		88,161
Senior Notes [Member] | 2035 IKE Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,035
Stated interest rate (percent)	6.50%
Principal Amount	$ 65,000		65,000
Unamortized Premium, Discount and Debt Issuance Costs,	(578)		(602)
Net, Long-term Debt	$ 64,422		64,398
Senior Notes [Member] | 5% Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2,046
Stated interest rate (percent)	5.00%
Principal Amount	$ 700,000		700,000
Unamortized Premium, Discount and Debt Issuance Costs,	(25,463)		(26,017)
Net, Long-term Debt	$ 674,537		$ 673,983

Long-Term Debt (Revolving Credi

Long-Term Debt (Revolving Credit Facility) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Principal amount	$ 3,352,889	$ 3,677,889
Line of Credit [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,000,000
Principal amount	0	$ 325,000
Letters of credit outstanding	45,414
Remaining borrowing capacity	$ 954,586
Minimum [Member] | LIBOR [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Minimum [Member] | Alternate Base Rate [Domain] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.00%
Maximum [Member] | LIBOR [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Maximum [Member] | Alternate Base Rate [Domain] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.75%

Long-Term Debt (Senior Notes) (

Long-Term Debt (Senior Notes) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Aug. 10, 2016
Debt Instrument [Line Items]
Principal amount	$ 3,352,889	$ 3,677,889
Unamortized Debt Issuance Costs	$ 21,547	$ 24,113
Senior Notes [Member] | 3.60% Percentage Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Principal amount			$ 750,000
Stated interest rate (percent)			3.60%
Senior Notes [Member] | 5.0% Percentage Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Principal amount			$ 700,000
Stated interest rate (percent)			5.00%

Long-Term Debt (Exchange Offers

Long-Term Debt (Exchange Offers) (Details) - USD ($) $ in Thousands	Apr. 24, 2017	Mar. 27, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Aug. 10, 2016
Debt Instrument [Line Items]
Principal amount			$ 3,352,889	$ 3,677,889
Senior Notes [Member] | 3.60% Percentage Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Principal amount						$ 750,000
Stated interest rate (percent)						3.60%
Exchange offer percentage		99.9667%
Senior Notes [Member] | 5.0% Percentage Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Principal amount						$ 700,000
Stated interest rate (percent)						5.00%
Exchange offer percentage		100.00%
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member]
Debt Instrument [Line Items]
Principal amount			$ 624,793	624,793	$ 624,793
Stated interest rate (percent)			4.625%		4.625%
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member]
Debt Instrument [Line Items]
Principal amount			$ 433,793	433,793	$ 433,793
Stated interest rate (percent)			4.875%		4.875%
Senior Notes [Member] | 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member]
Debt Instrument [Line Items]
Principal amount		$ 63,207	$ 63,207	63,207	$ 688,000
Stated interest rate (percent)		4.625%	4.625%		4.625%
Exchange offer percentage	100.00%
Senior Notes [Member] | 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member]
Debt Instrument [Line Items]
Principal amount		$ 16,207	$ 16,207	$ 16,207	$ 450,000
Stated interest rate (percent)		4.875%	4.875%		4.875%

Long-Term Debt (GO Zone Bonds)

Long-Term Debt (GO Zone Bonds) (Details) - Subsequent Event [Member] - Senior Notes [Member] - 2035 GO Zone 6 1/2% Notes [Member]	Nov. 01, 2017USD ($)
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	$ 250,000
Percentage of principal amount redeemed	100.00%

Pension and Post-Retirement B62

Pension and Post-Retirement Benefits (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Plan [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer			$ 8,108	$ 0
Service cost	$ 1,336	$ 315	4,007	315
Defined Benefit Plan, Plan Assets, Administration Expense	0	730	0	730
Interest cost	6,198	2,191	18,594	1,553
Expected return on plan assets	(9,976)	(3,800)	(29,928)	(5,260)
Amortization of net loss	297	338	892	978
Net periodic benefit cost (income)	(2,145)	(226)	(6,435)	(1,684)
Pension Plan [Member] | Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer			659	0
Service cost	528	318	1,509	777
Defined Benefit Plan, Plan Assets, Administration Expense	0	0	0	0
Interest cost	615	622	1,754	1,763
Expected return on plan assets	(162)	(50)	(466)	(50)
Amortization of net loss	217	0	663	0
Net periodic benefit cost (income)	1,198	890	3,460	2,490
Other Postretirement Benefits Plan [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	163	72	489	81
Interest cost	500	250	1,499	540
Amortization of net loss	15	31	45	94
Net periodic benefit cost (income)	678	353	2,033	715
Other Postretirement Benefits Plan [Member] | Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	1	41	1
Interest cost	35	3	100	3
Amortization of net loss	0	0	0	0
Net periodic benefit cost (income)	$ 49	$ 4	$ 141	$ 4

Pension and Post-Retirement B63

Pension and Post-Retirement Benefits (Additional Information) (Details) - Pension Plan [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	$ 8,108	$ 0
Estimated future employer contributions in current fiscal year	2,569
Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Contributions by Employer	659	$ 0
Estimated future employer contributions in current fiscal year	$ 143

Stockholders' Equity (Changes i

Stockholders' Equity (Changes in Stockholders Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 3,892,045	$ 3,561,931
Net income	$ 219,150	$ 70,014	523,278	314,570
Pension and other post- retirement benefits liability			1,013	409
Foreign currency translation adjustments			109,515	15,758
Other			(260)	4,999
Common stock repurchased				(66,725)
Shares issued—stock- based compensation			2,204	1,650
Stock-based compensation, net of tax on stock options exercised			10,223	7,778
Dividends declared			(76,491)	(71,933)
Distributions to noncontrolling interests			(20,767)	(12,300)
Issuance of Westlake Chemical Partners LP common units			110,739
Noncontrolling interest in acquired business				68,000
Ending balance	4,551,499	3,824,137	4,551,499	3,824,137
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,347	1,347
Shares issued—stock- based compensation			0	0
Ending balance	1,347	1,347	1,347	1,347
Common Stock, Held in Treasury [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(319,339)	(258,312)
Common stock repurchased				(66,725)
Shares issued—stock- based compensation			4,645	5,057
Ending balance	(314,694)	(319,980)	(314,694)	(319,980)
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			550,641	542,148
Shares issued—stock- based compensation			(2,441)	(3,407)
Stock-based compensation, net of tax on stock options exercised			10,223	7,778
Ending balance	558,423	546,519	558,423	546,519
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			3,412,286	3,109,987
Net income			501,849	299,914
Dividends declared			(76,491)	(71,933)
Ending balance	3,837,644	3,337,968	3,837,644	3,337,968
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(121,306)	(129,292)
Pension and other post- retirement benefits liability			1,057	409
Foreign currency translation adjustments			106,563	15,758
Other			(260)	4,999
Ending balance	(13,946)	(108,126)	(13,946)	(108,126)
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			368,416	296,053
Net income			21,429	14,656
Pension and other post- retirement benefits liability			(44)
Foreign currency translation adjustments			2,952
Distributions to noncontrolling interests			(20,767)	(12,300)
Issuance of Westlake Chemical Partners LP common units			110,739
Noncontrolling interest in acquired business				68,000
Ending balance	$ 482,725	$ 366,409	$ 482,725	$ 366,409

Stockholders' Equity (Changes65

Stockholders' Equity (Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss	$ (13,946)		$ (13,946)		$ (121,306)
Net other comprehensive income (loss) for the period	(39,878)	$ 26,025	(107,360)	$ (21,166)
Ending balance	4,551,499	3,824,137	4,551,499	3,824,137
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss					(121,306)	$ (129,292)
Other comprehensive income (loss) before reclassifications			106,303	73,056
Amounts reclassified from accumulated other comprehensive loss (income)			1,057	(51,890)
Net other comprehensive income (loss) for the period			(107,360)	(21,166)
Ending balance	(13,946)	(108,126)	(13,946)	(108,126)
Benefits Liability, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss					28,945	(8,607)
Other comprehensive income (loss) before reclassifications			0	(252)
Amounts reclassified from accumulated other comprehensive loss (income)			1,057	661
Net other comprehensive income (loss) for the period			(1,057)	(409)
Ending balance	30,002	(8,198)	30,002	(8,198)
Cumulative Foreign Currency Exchange, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss					(150,202)	(115,690)
Other comprehensive income (loss) before reclassifications			106,563	15,758
Amounts reclassified from accumulated other comprehensive loss (income)			0	0
Net other comprehensive income (loss) for the period			(106,563)	(15,758)
Ending balance	(43,639)	(99,932)	(43,639)	(99,932)
Net Unrealized Holdings Gains (Losses) on Investments, Net of Tax [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Accumulated other comprehensive loss					$ (49)	$ (4,995)
Other comprehensive income (loss) before reclassifications			(260)	57,550
Amounts reclassified from accumulated other comprehensive loss (income)			0	(52,551)
Net other comprehensive income (loss) for the period			260	(4,999)
Ending balance	$ (309)	$ 4	$ (309)	$ 4

Stockholders' Equity (Reclassif

Stockholders' Equity (Reclassifications in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for income taxes, investments	$ (108,619)	$ 6,552	$ (232,690)	$ (129,332)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total reclassifications for the period	(336)	51,477	(1,057)	51,890
Benefits Liability, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, before Tax	(529)	(369)	(1,600)	(1,072)
Other Comprehensive Income (Loss), Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	193	141	543	411
Other Comprehensive Income (Loss), Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	(336)	(228)	(1,057)	(661)
Total reclassifications for the period			(1,057)	(661)
Net Unrealized Holdings Gains on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total reclassifications for the period			0	52,551
Net Unrealized Holdings Gains on Available-for-sale Securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Realized Gain on available for sale investments	0	52,401	0	53,720
Provision for income taxes, investments	0	(696)	0	(1,169)
Income (loss), including portion attributable to noncontrolling interest	$ 0	$ 51,705	$ 0	$ 52,551

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Aug. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,972	$ 1,502	$ 16,740	$ 6,588
Axiall Corporation [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (in usd per share)					$ 33

Derivative Instruments (Narrati

Derivative Instruments (Narrative) (Details) - Not Designated as Hedging Instrument [Member] - Commodity Forward Contracts [Member]	9 Months Ended	12 Months Ended
	Sep. 30, 2017MMBTUgal	Dec. 31, 2016MMBTUgal
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | gal	138,600,000	257,000,000
Derivative, Nonmonetary Notional Amount, Energy Measure | MMBTU	12,500,000	8,500,000

Derivative Instruments (Impact

Derivative Instruments (Impact of Derivative Instruments on Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Commodity Forward Contracts [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 12,416	$ 14,986
Derivative Liability, Fair Value, Gross Liability	7,618	7,221
Accounts receivable, net [Member]
Derivative [Line Items]
Derivative Asset, Current	5,350	7,589
Derivative Asset, Fair Value, Gross Asset	7,335	7,727
Derivative Liability, Fair Value, Gross Liability	1,985	138
Accounts receivable, net [Member] | Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Asset, Current	793	1,498
Derivative Asset, Fair Value, Gross Asset	2,778	1,636
Derivative Liability, Fair Value, Gross Liability	1,985	138
Accounts receivable, net [Member] | Not Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Asset, Current	4,557	6,091
Derivative Asset, Fair Value, Gross Asset	4,557	6,091
Derivative Liability, Fair Value, Gross Liability	0	0
Deferred Charges and other assets, net [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent	4,336	5,249
Derivative Asset, Fair Value, Gross Asset	4,336	5,249
Derivative Liability, Fair Value, Gross Liability	0	0
Deferred Charges and other assets, net [Member] | Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Deferred Charges and other assets, net [Member] | Not Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent	4,336	5,249
Derivative Asset, Fair Value, Gross Asset	4,336	5,249
Derivative Liability, Fair Value, Gross Liability	0	0
Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Current	704	1,349
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	704	1,349
Accrued Liabilities [Member] | Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Liability, Current	0	0
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Accrued Liabilities [Member] | Not Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Liability, Current	704	1,349
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	704	1,349
Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Noncurrent	4,184	3,724
Derivative Asset, Fair Value, Gross Asset	745	2,010
Derivative Liability, Fair Value, Gross Liability	4,929	5,734
Other Liabilities [Member] | Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Liability, Noncurrent	1,410	436
Derivative Asset, Fair Value, Gross Asset	745	2,010
Derivative Liability, Fair Value, Gross Liability	2,155	2,446
Other Liabilities [Member] | Not Subject to Master Netting [Member]
Derivative [Line Items]
Derivative Liability, Noncurrent	2,774	3,288
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	$ 2,774	$ 3,288

Derivative Instruments (Impac70

Derivative Instruments (Impact of Derivative Instruments Not Designated as Fair Value Hedges) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Not Designated as Hedging Instrument [Member] | Cost of Sales [Member] | Commodity Forward Contracts [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 6,846	$ (7,840)	$ (2,756)	$ 7,784

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Assets and Liabilities Accounted at Fair Value on Recurring Basis) (Details) - Commodity Forward Contracts [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	$ 12,416	$ 14,986
Risk management liabilities - Commodity forward contracts	7,618	7,221
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	12,416	14,986
Risk management liabilities - Commodity forward contracts	7,618	7,221
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	233	878
Risk management liabilities - Commodity forward contracts	6,183	6,854
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk management assets - Commodity forward contracts	12,183	14,108
Risk management liabilities - Commodity forward contracts	$ 1,435	$ 367

Fair Value Measurements (Summ72

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Mar. 27, 2017	Dec. 31, 2016	Sep. 30, 2016
4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,021
Stated interest rate (percent)	4.625%			4.625%
4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,021
Stated interest rate (percent)	4.625%	4.625%		4.625%
3.60% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,022
Stated interest rate (percent)	3.60%
4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,023
Stated interest rate (percent)	4.875%			4.875%
4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,023
Stated interest rate (percent)	4.875%	4.875%		4.875%
3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,026
Stated interest rate (percent)	3.60%
Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,027
6 1/2% Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,029
Stated interest rate (percent)	6.50%
6 3/4% Senior Notes Due 2032 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,032
Stated interest rate (percent)	6.75%
2035 GO Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,035
Stated interest rate (percent)	6.50%
2035 IKE Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,035
Stated interest rate (percent)	6.50%
5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2,046
Stated interest rate (percent)	5.00%
Carrying Value [Member] | 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 646,674		$ 651,630
Carrying Value [Member] | 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	65,550		66,069
Carrying Value [Member] | 3.60% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	248,365		248,109
Carrying Value [Member] | 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	445,584		447,224
Carrying Value [Member] | 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	16,684		16,747
Carrying Value [Member] | 3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	739,969		739,243
Carrying Value [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	10,889		10,889
Carrying Value [Member] | 6 1/2% Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	99,139		99,084
Carrying Value [Member] | 6 3/4% Senior Notes Due 2032 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	249,395		248,117
Carrying Value [Member] | 2035 GO Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	88,194		88,161
Carrying Value [Member] | 2035 IKE Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	64,422		64,398
Carrying Value [Member] | 5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	674,537		673,983
Carrying Value [Member] | Unsecured Revolving Credit Facility [Member] | Line of Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility	0		325,000
Fair Value [Member] | 4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	646,486		650,847
Fair Value [Member] | 4.625% Senior Notes Due 2021 (Existing Axiall 2021 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	62,983		65,775
Fair Value [Member] | 3.60% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	255,733		251,725
Fair Value [Member] | 4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	452,004		451,301
Fair Value [Member] | 4.875% Senior Notes Due 2023 (Existing Axiall 2023 Notes) [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	16,842		16,501
Fair Value [Member] | 3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	749,570		722,055
Fair Value [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	10,889		10,889
Fair Value [Member] | 6 1/2% Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	113,789		112,433
Fair Value [Member] | 6 3/4% Senior Notes Due 2032 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	251,250		258,818
Fair Value [Member] | 2035 GO Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	100,936		100,323
Fair Value [Member] | 2035 IKE Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	73,908		73,270
Fair Value [Member] | 5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	760,739		691,712
Fair Value [Member] | Unsecured Revolving Credit Facility [Member] | Line of Credit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Revolving credit facility	$ 0		$ 325,000

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Effective income tax rate	33.10%	(10.30%)	30.80%	29.10%
U.S. federal statutory income tax rate	35.00%	35.00%	35.00%	35.00%

Earnings per Share (Schedule of

Earnings per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 210,832	$ 65,662	$ 501,849	$ 299,914
Net income attributable to participating securities	(1,117)	(294)	(2,630)	(1,347)
Net income attributable to common shareholders	$ 209,715	$ 65,368	$ 499,219	$ 298,567

Earnings per Share (Reconciliat

Earnings per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Weighted average common shares—basic	129,069,186	128,793,661	129,033,597	129,519,577
Incremental Shares From Assumed exercise of options	819,782	586,295	756,368	584,320
Weighted average common shares-diluted	129,888,968	129,379,956	129,789,965	130,103,897
Earnings per share attributable to Westlake Chemical Corporation: Basic	$ 1.62	$ 0.51	$ 3.87	$ 2.31
Earnings per share attributable to Westlake Chemical Corporation: Diluted	$ 1.61	$ 0.51	$ 3.85	$ 2.29

Earnings per Share (Additional

Earnings per Share (Additional Information) (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Number of options excluded from computation of diluted earnings per share	335,276	620,010	291,888	577,254

Supplemental Information ( Addi

Supplemental Information ( Additional Information) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accrued Liabilities [Abstract]
Accrued liabilities	$ 609,472		$ 537,483
Accrued rebates	110,862		72,187
Accrued Income Taxes	77,985		10,891
Accrued Liabilities Affiliates	30,609		$ 10,551
Increase (Decrease) in Capital Expenditure Accrual	$ 8,082	$ 23,878

Supplemental Information (Other

Supplemental Information (Other Income, Net) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Interest income	$ 644	$ 537	$ 1,578	$ 6,900
Dividend income	127	574	250	1,499
Acquisition-related financing costs	0	11,420	0	12,220
Foreign exchange currency loss, net	(3,197)	(1,281)	(9,483)	(2,435)
Gain realized on previously held shares of Axiall common stock	0	49,080	0	49,080
Gains from sales of securities, net	0	3,321	0	4,640
Income from non-consolidated subsidiaries	3,855	1,475	11,066	7,213
Other	629	(1,021)	3,180	(2,586)
Other income, net	$ 2,058	$ 41,265	$ 6,591	$ 52,091

Commitments and Contingencies (

Commitments and Contingencies (Additional Information) (Detail) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 31, 2016USD ($)	Sep. 30, 2017USD ($)settlement	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2016USD ($)	Jun. 17, 2015USD ($)
Environmental Loss Contingencies [Line Items]
Environmental Loss contingency accrual		$ 47,409			$ 48,817
Equity Method Investment, Ownership Percentage		100.00%
Pending Litigation [Member]
Environmental Loss Contingencies [Line Items]
Maximum Expected Damages	$ 167
LDEQ [Member] | Settled Litigation [Member]
Environmental Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party		$ 192
Number of claims settled | settlement		2
LDEQ [Member] | Pending Litigation [Member]
Environmental Loss Contingencies [Line Items]
Maximum Expected Damages		$ 100
Natrium [Member] | Axiall Corporation [Member] | Settled Litigation [Member]
Environmental Loss Contingencies [Line Items]
Payments for environmental loss contingencies				$ 449
Lake Charles, Louisiana [Member] | Axiall Corporation [Member] | Environmental Protection Agency [Member] | Settled Litigation [Member]
Environmental Loss Contingencies [Line Items]
Litigation Settlement, Amount Awarded to Other Party			$ 878
Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss		80,000
Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss		40,000
Unfavorable Regulatory Action [Member] | Culvert City, Kentucky and Lakes Charles, Louisiana [Member] | Environmental Protection Agency [Member] | Pending Litigation [Member]
Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		100
Affiliated Entity [Member] | LACC [Member]
Environmental Loss Contingencies [Line Items]
Due to Affiliate						$ 225,000
Equity Method Investment, Ownership Percentage						10.00%
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		$ 106,405

Segment Information (Additional

Segment Information (Additional Information) (Detail)	9 Months Ended
	Sep. 30, 2017Segment
Segment Reporting [Abstract]
Number of segments	2

Segment Information (Sales) (De

Segment Information (Sales) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Net sales	$ 2,108,889	$ 1,279,028	$ 6,030,666	$ 3,340,276
Income (loss) from operations	365,747	46,563	868,161	428,777
Depreciation and amortization	153,634	94,229	448,533	227,193
Other income (expense), net	2,058	41,265	6,591	52,091
Provision for (benefit from) income taxes	108,619	(6,552)	232,690	129,332
Capital expenditures	133,369	180,170	414,271	467,330
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net sales	2,108,889	1,279,028	6,030,666	3,340,276
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	502,243	497,365	1,534,472	1,422,869
Income (loss) from operations	165,438	118,475	488,532	408,274
Depreciation and amortization	35,029	36,649	111,244	95,582
Other income (expense), net	(184)	1,101	1,555	3,706
Provision for (benefit from) income taxes	58,218	31,956	152,482	136,429
Capital expenditures	20,960	96,469	70,043	285,359
Operating Segments [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,606,646	781,663	4,496,194	1,917,407
Income (loss) from operations	216,515	22,235	431,276	136,559
Depreciation and amortization	117,490	56,136	331,585	128,691
Other income (expense), net	(970)	(1,226)	1,087	1,722
Provision for (benefit from) income taxes	60,784	(3,912)	114,979	29,655
Capital expenditures	107,515	83,523	329,968	180,392
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	377,269	380,810	1,121,603	1,098,500
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	124,974	116,555	412,869	324,369
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,252,963	599,276	3,541,409	1,492,650
Operating Segments [Member] | Building Products [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	353,683	182,387	954,785	424,757
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(16,206)	(94,147)	(51,647)	(116,056)
Depreciation and amortization	1,115	1,444	5,704	2,920
Other income (expense), net	3,212	41,390	3,949	46,663
Provision for (benefit from) income taxes	(10,383)	(34,596)	(34,771)	(36,752)
Capital expenditures	4,894	178	14,260	1,579
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	106,982	32,744	291,529	88,575
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	106,722	30,614	290,658	85,856
Intersegment sales [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	$ 260	$ 2,130	$ 871	$ 2,719

Segment Information (Reconcilia

Segment Information (Reconciliation of Total Segment Income from Operations to Consolidated Income before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Abstract]
Income from operations	$ 365,747	$ 46,563	$ 868,161	$ 428,777
Interest expense	(40,036)	(24,366)	(118,784)	(36,966)
Other income (expense), net	2,058	41,265	6,591	52,091
Income before income taxes	$ 327,769	$ 63,462	$ 755,968	$ 443,902

Segment Information (Total Asse

Segment Information (Total Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 11,244,125	$ 10,890,253
Operating Segments [Member] | Olefins [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,015,888	2,092,617
Operating Segments [Member] | Vinyls [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	8,695,509	8,287,204
Corporate and other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 532,728	$ 510,432

Westlake Chemical Partners Of84

Westlake Chemical Partners Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 29, 2017	Apr. 29, 2015	Aug. 04, 2014	Sep. 30, 2017	Sep. 30, 2016
Class of Stock [Line Items]
Partners' Capital Account, Units, Sold in Public Offering	5,175,000		12,937,500
Sale of Unit Price Per Unit	$ 22		$ 24
Net proceeds from issuance of Westlake Chemical Partners LP common units	$ 110,739		$ 286,100	$ 110,739	$ 0
Payments of Stock Issuance Costs	$ 3,111
Payments of Derivative Issuance Costs			$ 24,400
Limited Partner [Member] | Westlake Chemical OpCo LP [Member]
Class of Stock [Line Items]
Limited Partnership Ownership Percentage Increase	5.00%	2.70%
Limited Partner [Member] | Westlake Chemical OpCo LP [Member] | Subsidiary of Common Parent [Member] | IPO [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest	81.70%		89.40%
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	18.30%		10.60%
Limited Partner [Member] | Westlake Chemical Partners LP [Member] | Subsidiary of Common Parent [Member] | IPO [Member]
Class of Stock [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest			47.80%

Guarantor Disclosures (Addition

Guarantor Disclosures (Additional Information) (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Condensed Financial Statements, Captions [Line Items]
Equity Method Investment, Ownership Percentage	100.00%
3.60%, 5.0%, 4.625%, 4.875% Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Minimum debt amount guaranteed by subsidiaries	$ 5,000
3.60% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2,022
3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2,026
5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2,046
4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2,021
4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2,023

Guarantor Disclosures (Condense

Guarantor Disclosures (Condensed Consolidating Financial Information Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 678,233	$ 459,453	$ 380,519	$ 662,525
Accounts receivable, net	1,142,979	938,743
Inventories	834,835	801,100
Prepaid expenses and other current assets	34,860	48,493
Restricted cash	8,626	160,527
Total current assets	2,699,533	2,408,316
Property, plant and equipment, net	6,343,637	6,420,062
Goodwill	1,011,342	946,553
Customer relationships, net	635,884	611,615
Other intangible assets, net	166,166	175,839
Deferred charges and other assets, net	387,563	327,868
Total other assets, net	2,200,955	2,061,875
Total assets	11,244,125	10,890,253
Accounts payable	560,804	496,259
Accrued liabilities	609,472	537,483
Term loan	0	149,341
Total current liabilities	1,170,276	1,183,083
Long-term debt, net	3,349,402	3,678,654
Deferred income taxes	1,660,914	1,650,575
Pension and other post-retirement benefits	512,034	485,896
Total liabilities	6,692,626	6,998,208
Total Westlake Chemical Corporation stockholders' equity	4,068,774	3,523,629
Noncontrolling interests	482,725	368,416
Total equity	4,551,499	3,892,045	3,824,137	3,561,931
Total liabilities and equity	11,244,125	10,890,253
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	(6,398,674)	(4,832,599)
Inventories	0	0
Prepaid expenses and other current assets	(35,906)	(36,504)
Restricted cash	0	0
Total current assets	(6,434,580)	(4,869,103)
Property, plant and equipment, net	0	0
Goodwill	0	0
Customer relationships, net	0	0
Other intangible assets, net	0	(25,581)
Deferred charges and other assets, net	(11,426,403)	(10,832,054)
Total other assets, net	(11,426,403)	(10,857,635)
Total assets	(17,860,983)	(15,726,738)
Accounts payable	(6,220,016)	(4,807,780)
Accrued liabilities	(214,564)	(61,323)
Term loan		0
Total current liabilities	(6,434,580)	(4,869,103)
Long-term debt, net	(4,464,598)	(3,997,070)
Deferred income taxes	(22,882)	(22,494)
Pension and other post-retirement benefits	0	0
Total liabilities	(10,922,060)	(8,888,667)
Total Westlake Chemical Corporation stockholders' equity	(6,938,923)	(6,838,071)
Noncontrolling interests	0	0
Total equity	(6,938,923)	(6,838,071)
Total liabilities and equity	(17,860,983)	(15,726,738)
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	334,111	146,990	144,899	303,131
Accounts receivable, net	3,060,591	2,117,540
Inventories	0	0
Prepaid expenses and other current assets	16,616	30,748
Restricted cash	0	0
Total current assets	3,411,318	2,295,278
Property, plant and equipment, net	0	0
Goodwill	0	0
Customer relationships, net	0	0
Other intangible assets, net	0	0
Deferred charges and other assets, net	9,890,164	9,170,042
Total other assets, net	9,890,164	9,170,042
Total assets	13,301,482	11,465,320
Accounts payable	5,821,323	4,330,375
Accrued liabilities	155,106	26,367
Term loan		0
Total current liabilities	5,976,429	4,356,742
Long-term debt, net	3,256,280	3,584,949
Deferred income taxes	0	0
Pension and other post-retirement benefits	0	0
Total liabilities	9,232,709	7,941,691
Total Westlake Chemical Corporation stockholders' equity	4,068,773	3,523,629
Noncontrolling interests	0	0
Total equity	4,068,773	3,523,629
Total liabilities and equity	13,301,482	11,465,320
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	33,089	53,006	22,602	6,818
Accounts receivable, net	4,048,824	3,329,871
Inventories	631,322	597,819
Prepaid expenses and other current assets	31,785	41,755
Restricted cash	1,275	0
Total current assets	4,746,295	4,022,451
Property, plant and equipment, net	4,330,104	4,475,943
Goodwill	854,896	791,706
Customer relationships, net	493,960	468,645
Other intangible assets, net	92,155	130,243
Deferred charges and other assets, net	551,732	874,003
Total other assets, net	1,992,743	2,264,597
Total assets	11,069,142	10,762,991
Accounts payable	830,824	748,364
Accrued liabilities	436,816	389,216
Term loan		0
Total current liabilities	1,267,640	1,137,580
Long-term debt, net	4,334,142	4,090,775
Deferred income taxes	1,577,209	1,581,260
Pension and other post-retirement benefits	364,011	360,622
Total liabilities	7,543,002	7,170,237
Total Westlake Chemical Corporation stockholders' equity	3,526,140	3,592,754
Noncontrolling interests	0	0
Total equity	3,526,140	3,592,754
Total liabilities and equity	11,069,142	10,762,991
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	311,033	259,457	$ 213,018	$ 352,576
Accounts receivable, net	432,238	323,931
Inventories	203,513	203,281
Prepaid expenses and other current assets	22,365	12,494
Restricted cash	7,351	160,527
Total current assets	976,500	959,690
Property, plant and equipment, net	2,013,533	1,944,119
Goodwill	156,446	154,847
Customer relationships, net	141,924	142,970
Other intangible assets, net	74,011	71,177
Deferred charges and other assets, net	1,372,070	1,115,877
Total other assets, net	1,744,451	1,484,871
Total assets	4,734,484	4,388,680
Accounts payable	128,673	225,300
Accrued liabilities	232,114	183,223
Term loan		149,341
Total current liabilities	360,787	557,864
Long-term debt, net	223,578	0
Deferred income taxes	106,587	91,809
Pension and other post-retirement benefits	148,023	125,274
Total liabilities	838,975	774,947
Total Westlake Chemical Corporation stockholders' equity	3,412,784	3,245,317
Noncontrolling interests	482,725	368,416
Total equity	3,895,509	3,613,733
Total liabilities and equity	$ 4,734,484	$ 4,388,680

Guarantor Disclosures (Conden87

Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net sales	$ 2,108,889	$ 1,279,028	$ 6,030,666	$ 3,340,276
Cost of sales	1,610,837	1,076,895	4,759,637	2,641,192
Gross profit	498,052	202,133	1,271,029	699,084
Selling, general and administrative expenses	125,642	72,729	379,919	179,757
Transaction and integration-related costs	6,663	82,841	22,949	90,550
Income (loss) from operations	365,747	46,563	868,161	428,777
Interest expense	(40,036)	(24,366)	(118,784)	(36,966)
Other income (expense), net	2,058	41,265	6,591	52,091
Income before income taxes	327,769	63,462	755,968	443,902
Provision for (benefit from) income taxes	108,619	(6,552)	232,690	129,332
Equity in net income of subsidiaries	0	0	0	0
Net income	219,150	70,014	523,278	314,570
Net income attributable to noncontrolling interests	8,318	4,352	21,429	14,656
Net income attributable to Westlake Chemical Corporation	210,832	65,662	501,849	299,914
Comprehensive income attributable to Westlake Chemical Corporation	254,400	39,637	613,350	321,080
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	(432,733)	(317,892)	(1,227,878)	(961,567)
Cost of sales	(426,100)	(312,763)	(1,207,567)	(945,967)
Gross profit	(6,633)	(5,129)	(20,311)	(15,600)
Selling, general and administrative expenses	(6,633)	(5,129)	(20,311)	(15,600)
Transaction and integration-related costs	0	0	0	0
Income (loss) from operations	0	0	0	0
Interest expense	44,791	20,879	135,043	47,009
Other income (expense), net	(44,791)	(20,879)	(135,043)	(47,009)
Income before income taxes	0	0	0	0
Provision for (benefit from) income taxes	0	0	0	0
Equity in net income of subsidiaries	(212,989)	(52,391)	(505,981)	(297,715)
Net income	(212,989)	(52,391)	(505,981)	(297,715)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	(212,989)	(52,391)	(505,981)	(297,715)
Comprehensive income attributable to Westlake Chemical Corporation	(256,615)	(40,015)	(404,443)	(318,214)
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	0	0	0	0
Cost of sales	0	0	0	0
Gross profit	0	0	0	0
Selling, general and administrative expenses	1,509	2,092	2,429	3,648
Transaction and integration-related costs	0	0	0	0
Income (loss) from operations	(1,509)	(2,092)	(2,429)	(3,648)
Interest expense	(38,811)	(22,130)	(115,156)	(43,228)
Other income (expense), net	37,563	35,405	112,002	40,807
Income before income taxes	(2,757)	11,183	(5,583)	(6,069)
Provision for (benefit from) income taxes	(599)	(2,088)	(1,451)	(8,268)
Equity in net income of subsidiaries	212,989	52,391	505,981	297,715
Net income	210,831	65,662	501,849	299,914
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	210,831	65,662	501,849	299,914
Comprehensive income attributable to Westlake Chemical Corporation	254,400	39,636	613,350	321,079
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	1,704,086	984,937	4,880,682	2,567,232
Cost of sales	1,371,813	892,198	4,077,633	2,233,395
Gross profit	332,273	92,739	803,049	333,837
Selling, general and administrative expenses	93,149	47,952	281,412	121,261
Transaction and integration-related costs	6,387	82,687	22,611	90,396
Income (loss) from operations	232,737	(37,900)	499,026	122,180
Interest expense	(44,381)	(22,207)	(133,048)	(39,693)
Other income (expense), net	2,517	(15,189)	2,944	(22,291)
Income before income taxes	190,873	(75,296)	368,922	60,196
Provision for (benefit from) income taxes	92,597	(11,080)	198,054	106,792
Equity in net income of subsidiaries	0	0	0	0
Net income	98,276	(64,216)	170,868	(46,596)
Net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to Westlake Chemical Corporation	98,276	(64,216)	170,868	(46,596)
Comprehensive income attributable to Westlake Chemical Corporation	98,455	(64,113)	171,413	(46,187)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net sales	837,536	611,983	2,377,862	1,734,611
Cost of sales	665,124	497,460	1,889,571	1,353,764
Gross profit	172,412	114,523	488,291	380,847
Selling, general and administrative expenses	37,617	27,814	116,389	70,448
Transaction and integration-related costs	276	154	338	154
Income (loss) from operations	134,519	86,555	371,564	310,245
Interest expense	(1,635)	(908)	(5,623)	(1,054)
Other income (expense), net	6,769	41,928	26,688	80,584
Income before income taxes	139,653	127,575	392,629	389,775
Provision for (benefit from) income taxes	16,621	6,616	36,087	30,808
Equity in net income of subsidiaries	0	0	0	0
Net income	123,032	120,959	356,542	358,967
Net income attributable to noncontrolling interests	8,318	4,352	21,429	14,656
Net income attributable to Westlake Chemical Corporation	114,714	116,607	335,113	344,311
Comprehensive income attributable to Westlake Chemical Corporation	$ 158,160	$ 104,129	$ 233,030	$ 364,402

Guarantor Disclosures (Conden88

Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) - USD ($) $ in Thousands	Sep. 29, 2017	Aug. 04, 2014	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net income			$ 219,150	$ 70,014	$ 523,278	$ 314,570
Depreciation and amortization			153,634	94,229	448,533	227,193
Deferred income taxes					23,294	105,910
Net changes in working capital and other					(32,441)	(103,513)
Net cash provided by (used for) operating activities					962,664	544,160
Acquisition of business, net of cash acquired					0	(2,437,829)
Additions to property, plant and equipment			(133,369)	(180,170)	(414,271)	(467,330)
Additions to cost method investment					(47,000)	(4,000)
Proceeds from disposition of assets					171	213
Proceeds from involuntary conversion of assets					1,672	0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities					0	662,938
Purchase of securities					0	(138,422)
Settlements of derivative instruments					(7)	(4,655)
Net cash used for investing activities					(459,435)	(2,389,085)
Intercompany financing					0	0
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					(376)	(35,207)
Dividends paid					(76,491)	(71,933)
Distributions to noncontrolling interests					(20,767)	(12,300)
Proceeds from debt issuance					0	1,428,512
Net proceeds from issuance of Westlake Chemical Partners LP common units	$ 110,739	$ 286,100			110,739	0
Proceeds from issuance of notes payable					5,946	5,597
Proceeds from term loan and drawdown of revolver					225,000	600,000
Restricted cash associated with term loan					154,000	(154,000)
Repayment of term loan					(150,000)	0
Repayment of notes payable					(6,695)	(10,602)
Repayment of revolver					(550,000)	(125,000)
Repurchase of common stock for treasury					0	(67,406)
Other					2,204	2,840
Net cash provided by (used for) financing activities					(306,440)	1,560,501
Effect of exchange rate changes on cash and cash equivalents					21,991	2,418
Net increase (decrease) in cash and cash equivalents					218,780	(282,006)
Cash and cash equivalents at beginning of period					459,453	662,525
Cash and cash equivalents at end of period			678,233	380,519	678,233	380,519
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			(212,989)	(52,391)	(505,981)	(297,715)
Depreciation and amortization					0	0
Deferred income taxes					0	0
Net changes in working capital and other					505,981	297,715
Net cash provided by (used for) operating activities					0	0
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					0	0
Additions to cost method investment					0	0
Proceeds from disposition of assets					0	0
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					119,000
Proceeds from sales and maturities of securities						0
Purchase of securities						0
Settlements of derivative instruments					0	0
Net cash used for investing activities					119,000	0
Intercompany financing					0	0
Receivable under Investment Management Agreement Financing Activity					(119,000)
Debt issuance costs					0	0
Dividends paid					0	0
Distributions to noncontrolling interests					0	0
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					0	0
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					0	0
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(119,000)	0
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) 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	0	0
Westlake Chemical Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			210,831	65,662	501,849	299,914
Depreciation and amortization					0	0
Deferred income taxes					(217)	(5,178)
Net changes in working capital and other					(532,120)	(313,676)
Net cash provided by (used for) operating activities					(30,488)	(18,940)
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					0	0
Additions to cost method investment					0	0
Proceeds from disposition of assets					0	0
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities						658,338
Purchase of securities						(138,422)
Settlements of derivative instruments					0	0
Net cash used for investing activities					0	519,916
Intercompany financing					498,272	(2,242,604)
Receivable under Investment Management Agreement Financing Activity					119,000
Debt issuance costs					(376)	(33,617)
Dividends paid					(76,491)	(71,933)
Distributions to noncontrolling interests					0	0
Proceeds from debt issuance						1,428,512
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					225,000	450,000
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					0	0
Repayment of revolver					(550,000)	(125,000)
Repurchase of common stock for treasury						(67,406)
Other					2,204	2,840
Net cash provided by (used for) financing activities					217,609	(659,208)
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) in cash and cash equivalents					187,121	(158,232)
Cash and cash equivalents at beginning of period					146,990	303,131
Cash and cash equivalents at end of period			334,111	144,899	334,111	144,899
100% Owned Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			98,276	(64,216)	170,868	(46,596)
Depreciation and amortization					294,227	118,645
Deferred income taxes					20,299	100,908
Net changes in working capital and other					(129,330)	(39,859)
Net cash provided by (used for) operating activities					356,064	133,098
Acquisition of business, net of cash acquired						(2,437,829)
Additions to property, plant and equipment					(294,138)	(162,288)
Additions to cost method investment					(47,000)	(4,000)
Proceeds from disposition of assets					25	48
Proceeds from involuntary conversion of assets					0
Receivable under Investment Management Agreement					0
Proceeds from sales and maturities of securities						0
Purchase of securities						0
Settlements of derivative instruments					(7)	(4,655)
Net cash used for investing activities					(341,120)	(2,608,724)
Intercompany financing					(313,276)	2,289,200
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					0	0
Dividends paid					0	0
Distributions to noncontrolling interests					279,203	202,210
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					0
Proceeds from issuance of notes payable					0	0
Proceeds from term loan and drawdown of revolver					0	0
Restricted cash associated with term loan					0	0
Repayment of term loan					0
Repayment of notes payable					(788)	0
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(34,861)	2,491,410
Effect of exchange rate changes on cash and cash equivalents					0	0
Net increase (decrease) in cash and cash equivalents					(19,917)	15,784
Cash and cash equivalents at beginning of period					53,006	6,818
Cash and cash equivalents at end of period			33,089	22,602	33,089	22,602
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Net income			123,032	120,959	356,542	358,967
Depreciation and amortization					154,306	108,548
Deferred income taxes					3,212	10,180
Net changes in working capital and other					123,028	(47,693)
Net cash provided by (used for) operating activities					637,088	430,002
Acquisition of business, net of cash acquired						0
Additions to property, plant and equipment					(120,133)	(305,042)
Additions to cost method investment					0	0
Proceeds from disposition of assets					146	165
Proceeds from involuntary conversion of assets					1,672
Receivable under Investment Management Agreement					(119,000)
Proceeds from sales and maturities of securities						4,600
Purchase of securities						0
Settlements of derivative instruments					0	0
Net cash used for investing activities					(237,315)	(300,277)
Intercompany financing					(184,996)	(46,596)
Receivable under Investment Management Agreement Financing Activity					0
Debt issuance costs					0	(1,590)
Dividends paid					0	0
Distributions to noncontrolling interests					(299,970)	(214,510)
Proceeds from debt issuance						0
Net proceeds from issuance of Westlake Chemical Partners LP common units					110,739
Proceeds from issuance of notes payable					5,946	5,597
Proceeds from term loan and drawdown of revolver					0	150,000
Restricted cash associated with term loan					154,000	(154,000)
Repayment of term loan					(150,000)
Repayment of notes payable					(5,907)	(10,602)
Repayment of revolver					0	0
Repurchase of common stock for treasury						0
Other					0	0
Net cash provided by (used for) financing activities					(370,188)	(271,701)
Effect of exchange rate changes on cash and cash equivalents					21,991	2,418
Net increase (decrease) in cash and cash equivalents					51,576	(139,558)
Cash and cash equivalents at beginning of period					259,457	352,576
Cash and cash equivalents at end of period			$ 311,033	$ 213,018	$ 311,033	$ 213,018