10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-Q

x	QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
	For the quarterly period ended September 30, 2017

or

¨	TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934
	For the Transition Period from                    to

Commission File No. 001-32260

Westlake Chemical Corporation

(Exact name of Registrant as specified in its charter)

Delaware	76-0346924
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification Number)

2801 Post Oak Boulevard, Suite 600

Houston, Texas 77056

(Address of principal executive offices, including zip code)

(713) 960-9111

(Registrant's telephone number, including area code)

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.     YesxNo¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).     YesxNo¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a smaller reporting company, or an emerging growth company. See definitions of "large accelerated filer," "accelerated filer", "smaller reporting company" and "emerging growth company" in Rule 12b-2 of the Exchange Act (Check one):

Large accelerated filer	x	Accelerated filer	¨
Non-accelerated filer	¨  (Do not check if a smaller reporting company)	Smaller reporting company	¨
		Emerging growth company	¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act)     Yes¨Nox

The number of shares outstanding of the registrant's sole class of common stock as of October 31, 2017 was 129,107,447.

INDEX

Item	Page
PART I. FINANCIAL INFORMATION
1) Financial Statements	1
2) Management's Discussion and Analysis of Financial Condition and Results of Operations	39
3) Quantitative and Qualitative Disclosures about Market Risk	53
4) Controls and Procedures	55
PART II. OTHER INFORMATION
1) Legal Proceedings	56
1A) Risk Factors	56
2) Unregistered Sales of Equity Securities and Use of Proceeds	56
6) Exhibits	57

PART I. FINANCIAL INFORMATION

Item 1. Financial Statements

WESTLAKE CHEMICAL CORPORATION

CONSOLIDATED BALANCE SHEETS

(Unaudited)

	September 30, 2017			December 31, 2016
	(in thousands of dollars, except par values and share amounts)
ASSETS
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
LIABILITIES AND EQUITY
Current liabilities
Accounts payable	$	560,804		$	496,259
Accrued liabilities	609,472			537,483
Term loan	—			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
Commitments and contingencies (Note 18)
Stockholders' equity
Preferred stock, $0.01 par value, 50,000,000 shares authorized; no shares issued and outstanding	—			—
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

The accompanying notes are an integral part of these consolidated financial statements.

1

WESTLAKE CHEMICAL CORPORATION

CONSOLIDATED STATEMENTS OF OPERATIONS

(Unaudited)

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(in thousands of dollars, except per share data and share amounts)
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 from operations	365,747			46,563			868,161			428,777
Other income (expense)
Interest expense	(40,036		)	(24,366		)	(118,784		)	(36,966		)
Other income, 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
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	$	1.62		$	0.51		$	3.87		$	2.31
Diluted	$	1.61		$	0.51		$	3.85		$	2.29
Weighted average common shares outstanding:
Basic	129,069,186			128,793,661			129,033,597			129,519,577
Diluted	129,888,968			129,379,956			129,789,965			130,103,897
Dividends per common share	$	0.2100		$	0.1906		$	0.5912		$	0.5536

The accompanying notes are an integral part of these consolidated financial statements.

2

WESTLAKE CHEMICAL CORPORATION

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME

(Unaudited)

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(in thousands of dollars)
Net income	$	219,150		$	70,014		$	523,278		$	314,570
Other comprehensive income (loss), net of income taxes
Pension and other post-retirement benefits liability
Pension and other post-retirement reserves    adjustment (excluding amortization)	—			(206		)	—			(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 adjustments
Foreign currency translation	39,714			6,453			108,166			15,758
Income tax provision on foreign currency    translation	(76		)	—			(1,603		)	—
Net unrealized holding gains (losses) on investments
Unrealized holding gains on investments	—			1,550			—			61,524
Reclassification of net realized gains to net    income	—			(52,401		)	—			(53,720		)
Income tax provision on available-for-sale    investments	—			18,270			—			(2,805		)
Other	(96		)	—			(260		)	—
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

The accompanying notes are an integral part of these consolidated financial statements.

3

WESTLAKE CHEMICAL CORPORATION

CONSOLIDATED STATEMENTS OF CASH FLOWS

(Unaudited)

	Nine Months Ended September 30,
	2017			2016
	(in thousands of dollars)
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	—			(53,720		)
Write-off of debt issuance costs	659			—
Deferred income taxes	23,294			105,910
Windfall tax benefits from share-based payment arrangements	—			(1,190		)
Dividends in excess of income from equity method investments	(2,132		)	(61		)
Gain on involuntary conversion of assets	(1,672		)	—
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 operating activities	962,664			544,160
Cash flows from investing activities
Acquisition of business, net of cash acquired	—			(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			—
Proceeds from sales and maturities of securities	—			662,938
Purchase of securities	—			(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			—
Proceeds from debt issuance	—			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		)	—
Repayment of notes payable	(6,695		)	(10,602		)
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	(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

The accompanying notes are an integral part of these consolidated financial statements.

4

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

1. 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.

5

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

6

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

7

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

8

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

2. 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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

3. 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		)

4. Accounts Receivable

Accounts receivable consist of the following:

	September 30, 2017			December 31, 2016
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

5. Inventories

Inventories consist of the following:

	September 30, 2017		December 31, 2016
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

6. 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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

7. 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.

8. 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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

9. Long-Term Debt

Long-term debt consists of the following:

	September 30, 2017							December 31, 2016
	Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt		Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt
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.

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

10. 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.

15

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans
Service cost	$	1,336		$	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. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans
Service cost	$	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

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WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

11. 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

17

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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	)

18

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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.

12. 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.

19

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

13. 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.

20

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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 arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	4,336			4,336		—
	4,336			4,336		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(704		)	—		(704		)
	(704		)	—		(704		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(1,410		)	745		(2,155		)
Derivative positions not subject to enforceable master netting arrangements	(2,774		)	—		(2,774		)
	(4,184		)	745		(4,929		)
Risk management assets (liabilities)—Commodity forward    contracts				$	12,416	$	(7,618	)

21

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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 arrangements	$	1,498		$	1,636	$	(138	)
Derivative positions not subject to enforceable master netting arrangements	6,091			6,091		—
	7,589			7,727		(138		)
Deferred charges and other assets, net
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	5,249			5,249		—
	5,249			5,249		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(1,349		)	—		(1,349		)
	(1,349		)	—		(1,349		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(436		)	2,010		(2,446		)
Derivative positions not subject to enforceable master netting arrangements	(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.

14. 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.

22

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share 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

23

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

15. 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.

16. 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

24

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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.

17. 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

25

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

18. 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.

26

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

• 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.

19. 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

27

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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

28

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	September 30, 2017		December 31, 2016
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

20. 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.

21. Subsequent Events

Subsequent events were evaluated through the date on which the consolidated financial statements were issued.

22. 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.

29

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

30

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

31

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

32

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

33

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

34

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

35

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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		)

36

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

	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

37

WESTLAKE CHEMICAL CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS—Continued

(Unaudited)

(in thousands of dollars, except share amounts and per share data)

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

38

Item 2. Management's Discussion and Analysis of Financial Condition and Results of Operations

This discussion and analysis should be read in conjunction with information contained in the accompanying unaudited consolidated interim financial statements of Westlake Chemical Corporation ("Westlake") and the notes thereto and the consolidated financial statements and notes thereto of Westlake Chemical Corporation included in Westlake Chemical Corporation's Annual Report on Form 10-K for the fiscal year ended December 31, 2016 (the "2016 Form 10-K"). The following discussion contains forward-looking statements. Please read "Forward-Looking Statements" for a discussion of limitations inherent in such statements.

We are a vertically integrated global manufacturer and marketer of petrochemicals, polymers and building products. Our two principal operating segments are Olefins and Vinyls. We use a majority of our internally-produced basic chemicals to produce higher value-added chemicals and building products.

Since 2009 and continuing through the third quarter of 2017, a cost advantage for ethane-based ethylene producers over naphtha-based ethylene producers has allowed a strong export market for polyethylene and ethylene derivatives and higher margins for North American chemical producers, including Westlake. However, the falling crude oil prices in recent years have resulted in reduced prices and margins. Continued strong global demand for polyethylene has resulted in improved operating margins and cash flows for our Olefins segment in recent years. However, we have seen a significant reduction in the cost advantage enjoyed by North American ethane-based ethylene producers due to lower crude oil prices, beginning in the third quarter of 2014 and continuing through the third quarter of 2017. Looking forward, new ethylene and polyethylene capacity additions in North America, Asia and the Middle East, and a number of new capacities announced in recent years, may lead to periods of over-supply and lower profitability. As a result, our Olefins segment operating margins may be negatively impacted.

Since the 2008 housing market collapse, continued slow recovery in the U.S. construction markets and budgetary constraints in municipal spending have contributed to lower North American demand for our vinyls products, which have negatively impacted our Vinyls segment operating rates and margins. However, since late 2010, the PVC industry in the U.S. has experienced an increase in PVC resin exports, driven largely by more competitive feedstock and energy cost positions in the U.S. As a consequence, the U.S. PVC resin industry operating rates have improved since 2010. In addition, our July 2014 acquisition of Vinnolit Holdings GmbH and its subsidiary companies ("Vinnolit"), an integrated global leader in specialty PVC resins, has contributed to improved operating margins and cash flows for our Vinyls segment. Globally, there were large chlor-alkali capacity additions between 2008 and 2015 resulting in excess capacity and lower industry operating rates which exerted downward pressure on caustic soda pricing. Announced capacity is now complete and increasing demand driven by the improving economic growth and U.S. producers' competitive export position is expected to result in improved operating rates and caustic soda pricing. On August 31, 2016, we completed the acquisition of Axiall Corporation ("Axiall") for $33.00 per share in an all-cash transaction (the "Merger"). The combined company is the third-largest global chlor-alkali producer and the third-largest PVC producer in the world. Westlake is the second-largest purchaser of ethylene in the U.S. and lower prices could positively impact our Vinyls segment.

The economic environment in the U. S. and globally appears to be improving. However, depending on the performance of the global economy in the remainder of 2017 and beyond, our financial condition, results of operations or cash flows could be negatively impacted.

Non-GAAP Financial Measures

The body of accounting principles generally accepted in the United States is commonly referred to as "U.S. GAAP." For this purpose, a non-GAAP financial measure is generally defined by the Securities and Exchange Commission ("SEC") as one that purports to measure historical or future financial performance, financial position or cash flows, but excludes or includes amounts that would not be so adjusted in the most comparable GAAP measures. In this report, we disclose non-GAAP financial measures, primarily earnings before interest, taxes, depreciation and amortization ("EBITDA"). EBITDA is calculated as net income before interest expense, income taxes, depreciation and amortization. The non-GAAP financial measures described in this Form 10-Q are not substitutes for the GAAP measures of earnings and cash flow.

39

EBITDA is included in this Form 10-Q because our management considers it an important supplemental measure of our performance and believes that it is frequently used by securities analysts, investors and other interested parties in the evaluation of companies in our industry, some of which present EBITDA when reporting their results. We regularly evaluate our performance as compared to other companies in our industry that have different financing and capital structures and/or tax rates by using EBITDA. In addition, we utilize EBITDA in evaluating acquisition targets. Management also believes that EBITDA is a useful tool for measuring our ability to meet our future debt service, capital expenditures and working capital requirements, and EBITDA is commonly used by us and our investors to measure our ability to service indebtedness. EBITDA is not a substitute for the GAAP measures of earnings or of cash flow and is not necessarily a measure of our ability to fund our cash needs. In addition, it should be noted that companies calculate EBITDA differently and, therefore, EBITDA as presented for us may not be comparable to EBITDA reported by other companies. EBITDA has material limitations as a performance measure because it excludes interest expense, depreciation and amortization, and income taxes.

Recent Developments

On September 29, 2017, Westlake Chemical Partners, LP ("WLKP") completed a secondary offering of 5,175,000 common units at a price of $22.00 per unit and purchased an additional 5.0% newly-issued limited partner interest in Westlake Chemical OpCo LP ("OpCo") for approximately $229.2 million resulting in an aggregate 18.3% limited partner interest in OpCo effective July 1, 2017. Net proceeds to WLKP from the sale of the units was $110.7 million, net of underwriting discounts, structuring fees and estimated offering expenses of approximately $3.1 million. WLKP used the proceeds from the offering and the existing revolving credit facility with Westlake Chemical Finance Corporation, our subsidiary, to fund the purchase of the additional 5.0% interest in OpCo.

During September 2017, we directed the Louisiana Local Government Authority Environmental Facilities and Community Development Authority (the “Authority”) to optionally redeem in full $250.0 million aggregate principal amount of the 2007 Series revenue bonds (the “GO Zone Bonds”) on November 1, 2017 at a redemption price of par, plus accrued and unpaid interest, if any, to the redemption date. 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 at any time on or after November 1, 2017 for 100.0% of the principal plus accrued unpaid interest, if any. 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 of $250.0 million, to the Senior Notes trustee for cancellation. We used cash on hand to fund the redemption of the GO Zone Bonds.

On August 30, 2017, following WLKP's cash distribution for the second quarter of 2017, the requirement under WLKP's partnership agreement for the conversion of all subordinated units was satisfied. As a result, effective August 30, 2017, the 12,686,115 subordinated units owned by us were converted into common units on a one-for-one basis and thereafter participate on terms equal with all other common units in distributions of available cash.

On August 1, 2017, the Company, WLKP and OpCo executed an Investment Management Agreement (the "Investment Management Agreement") that authorized Westlake to invest the Partnership's and OpCo's excess cash.

On August 1, 2017, our wholly owned subsidiary, Westlake Chemical Finance Corporation, entered into an amendment to the revolving credit facility with WLKP, resulting in the extension of the credit facility's maturity date from April 29, 2018 to April 29, 2021.

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Results of Operations

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(dollars in thousands, except per share data)
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
Total	$	2,108,889		$	1,279,028		$	6,030,666		$	3,340,276
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		)
Total income from operations	365,747			46,563			868,161			428,777
Interest expense	(40,036		)	(24,366		)	(118,784		)	(36,966		)
Other income, net	2,058			41,265			6,591			52,091
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
Diluted earnings per share	$	1.61		$	0.51		$	3.85		$	2.29
EBITDA (1)	$	521,439		$	182,057		$	1,323,285		$	708,061

_____________

(1) See "Reconciliation of EBITDA to Net Income and to Net Cash Provided by Operating Activities" below.

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	Three Months Ended September 30, 2017				Nine Months Ended September 30, 2017
	Average Sales Price		Volume		Average Sales Price		Volume
Product sales price and volume percentage change    from prior-year period
Olefins	+1.8	%	-0.8	%	+9.2	%	-1.3	%
Vinyls	+18.7	%	+86.8	%	+17.8	%	+116.7	%
Company average	+12.1	%	+52.8	%	+14.1	%	+66.4	%
	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Average industry prices (1)
Ethane (cents/lb)	8.8		6.3		8.3		6.2
Propane (cents/lb)	18.2		11.2		16.6		10.7
Ethylene (cents/lb) (2)	24.7		32.5		27.8		26.5
Polyethylene (cents/lb) (3)	70.7		68.7		69.0		65.3
Styrene (cents/lb) (4)	85.1		66.8		85.0		63.3
Caustic soda ($/short ton) (5)	811.7		660.8		777.8		618.3
Chlorine ($/short ton) (6)	332.5		304.2		320.8		295.3
PVC (cents/lb) (7)	62.5		56.5		61.7		53.9

_____________

(1) Industry pricing data was obtained from IHS Chemical. We have not independently verified the data.

(2) Represents average North American spot prices of ethylene over the period as reported by IHS Chemical.

(3) Represents average North American net transaction prices of polyethylene low density GP-Film grade over the period as reported by IHS Chemical.

(4) Represents average North American contract prices of styrene over the period as reported by IHS Chemical.

(5) Represents average North American undiscounted contract prices of caustic soda over the period as reported by IHS Chemical.

(6) Represents average North American contract prices of chlorine (into chemicals) over the period as reported by IHS Chemical.

(7) Represents average North American contract prices of polyvinyl chloride (PVC) over the period as reported by IHS Chemical. Effective January 1, 2017, IHS Chemical made a non-market downward adjustment of 15 cents per pound to PVC prices. For comparability, we adjusted each prior-year period's PVC price downward by 15 cents per pound consistent with the IHS Chemical non-market adjustment.

Reconciliation of EBITDA to Net Income and to Net Cash Provided by Operating Activities

The following table presents the reconciliation of EBITDA to net income and to net cash provided by operating activities, the most directly comparable GAAP financial measures, for each of the periods indicated.

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
	(dollars in thousands)
Net cash provided by operating activities	$	482,950		$	174,268		$	962,664		$	544,160
Changes in operating assets and liabilities and other	(255,468		)	(101,334		)	(416,092		)	(123,680		)
Deferred income taxes	(8,332		)	(2,920		)	(23,294		)	(105,910		)
Net income	219,150			70,014			523,278			314,570
Add:
Depreciation and amortization	153,634			94,229			448,533			227,193
Interest expense	40,036			24,366			118,784			36,966
Provision for (benefit from) income taxes	108,619			(6,552		)	232,690			129,332
EBITDA	$	521,439		$	182,057		$	1,323,285		$	708,061

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Summary

For the quarter ended September 30, 2017, net income attributable to Westlake Chemical Corporation was $210.8 million, or $1.61 per diluted share, on net sales of $2,108.9 million. This represents an increase in net income attributable to Westlake Chemical Corporation of $145.1 million, or $1.10 per diluted share, compared to the third quarter of 2016 net income attributable to Westlake Chemical Corporation of $65.7 million, or $0.51 per diluted share, on net sales of $1,279.0 million. Net income for the third quarter of 2017 increased versus the prior-year period primarily due to (1) earnings contributed by Axiall, which was acquired on August 31, 2016; (2) lower transaction and integration-related costs associated with the acquisition; and (3) higher sales prices for major products resulting in improved margins. These increases, as compared to the third quarter of 2016, were partially offset by (1) higher interest expense due to the increased debt balance as a result of the Axiall acquisition; (2) a third quarter 2016 realized gain of $49.1 million from the previously held common stock of Axiall; and (3) a higher effective tax rate. Net sales for the third quarter of 2017increased by $829.9 million compared to net sales for the third quarter of 2016, mainly due to higher sales contributed by Axiall and higher sales prices for our major products. Income from operations was $365.7 million for the third quarter of 2017 as compared to $46.6 million for the third quarter of 2016. The increase in income from operations for the third quarter of 2017 was mainly a result of earnings contributed by Axiall, lower transaction and integration-related costs and higher sales prices as compared to the third quarter of 2016. Transaction and integration-related costs in the third quarter of 2017 were $6.7 million, or $0.03 per diluted share.

For the nine months ended September 30, 2017, net income attributable to Westlake Chemical Corporation was $501.8 million, or $3.85 per diluted share, on net sales of $6,030.7 million. This represents an increase in net income attributable to Westlake Chemical Corporation of $201.9 million, or $1.56 per diluted share, compared to the nine months ended September 30, 2016 net income attributable to Westlake Chemical Corporation of $299.9 million, or $2.29 per diluted share, on net sales of $3,340.3 million. Net income for the nine months ended September 30, 2017 increased versus the prior-year period primarily due to (1) earnings contributed by Axiall; (2) higher sales prices for our major products, resulting in improved margins; and (3) lower transaction and integration-related costs associated with the integration of Axiall. These increases versus the prior-year period were partially offset by higher interest expense due to the increased debt balance and the realized gain in the nine months ended September 30, 2016 of $49.1 million from the previously held common stock of Axiall. Net sales for the nine months ended September 30, 2017increased by $2,690.4 million compared to net sales for the nine months ended September 30, 2016, mainly due to higher sales contributed by Axiall, which was acquired on August 31, 2016, and higher sales prices for our major products. Income from operations was $868.2 million for the nine months ended September 30, 2017 as compared to $428.8 million for the nine months ended September 30, 2016. The increase in income from operations was mainly a result of earnings contributed by Axiall, higher sales prices for our major products and lower transaction and integration-related costs. Transaction and integration-related costs in the nine months ended September 30, 2017 were $22.9 million, or $0.12 per diluted share.

RESULTS OF OPERATIONS

Third Quarter 2017 Compared with Third Quarter 2016

Net Sales. Net sales increased by $829.9 million, or 64.9%, to $2,108.9 million in the third quarter of 2017 from $1,279.0 million in the third quarter of 2016, primarily attributable to sales contributed by Axiall, which was acquired on August 31, 2016, and higher sales prices. Average sales prices for the third quarter of 2017increased by 12.1% as compared to the third quarter of 2016. Overall sales volumes increased by 52.8% as compared to the third quarter of 2016, primarily attributable to sales contributed by Axiall, as compared to the prior-year period.

Gross Profit. Gross profit margin percentage increased to 23.6% in the third quarter of 2017 from 15.8% in the third quarter of 2016. The third quarter of 2017 gross profit margin was higher primarily due to higher sales volumes for caustic soda and PVC resin contributed by Axiall and an increase in sales prices for our major products as compared to the third quarter of 2016. The increase was partially offset by higher feedstock costs and higher energy prices, as compared to the third quarter of 2016.

Selling, General and Administrative Expenses. Selling, general and administrative expenses increased by $52.9 million to $125.6 million in the third quarter of 2017 as compared to $72.7 million in the third quarter of 2016. This increase was mainly due to selling, general and administrative expenses of Axiall which were primarily comprised of the amortization of intangible assets acquired on acquisition.

43

Transaction and Integration-related Costs. The transactions and integration-related costs were $6.7 million in the third quarter of 2017 as compared to $82.8 million in the third quarter of 2016. Transaction and integration-related costs were lower by $76.1 million in the third quarter of 2017 as compared to the third quarter of 2016 predominantly because significant transaction and integration-related costs were incurred at the time of the Merger in the third quarter of 2016. The transaction and integration costs for the third quarter of 2017 primarily consisted of severance benefits provided to former Axiall employees in conjunction with the Merger and integration costs and consulting fees related to the Merger. The transaction and integration-related costs for the third quarter of 2016 primarily consisted of severance benefits provided to former Axiall executives in conjunction with the Merger, including the conversion of Axiall restricted stock units into our restricted stock units, transitional service expenses for certain former Axiall employees, retention agreement costs and consulting and professional fees related to the Merger.

Interest Expense. Interest expense increased by $15.6 million to $40.0 million in the third quarter of 2017 from $24.4 million in the third quarter of 2016 primarily as a result of higher average debt outstanding for the period as well as decreased capitalized interest on major capital projects in the third quarter of 2017 as compared to the third quarter of 2016. The debt balance increased in August 2016 to finance the Merger. See "Liquidity and Capital Resources—Debt" below for further discussion on our indebtedness.

Other Income (Expense), Net. Other income, net decreased by $39.2 million to income of $2.1 million in the third quarter of 2017 from income of $41.3 million in the third quarter of 2016. The decrease was primarily attributable to the realized gain in the third quarter of 2016 of $49.1 million from the previously held common stock of Axiall.

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 tax rate, which was a benefit, was (10.3)% for the 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, 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.

Olefins Segment

Net Sales. Net sales for the Olefins segment increased by $4.8 million, or 1.0%, to $502.2 million in the third quarter of 2017 from $497.4 million in the third quarter of 2016, primarily due to higher sales prices. Average sales volumes for the Olefins segment decreased by 0.8% in the third quarter of 2017 as compared to the third quarter of 2016. Average sales prices for the Olefins segment increased by 1.8% in the third quarter of 2017 as compared to the third quarter of 2016.

Income from Operations. Income from operations for the Olefins segment increased by $46.9 million to $165.4 million in the third quarter of 2017 from $118.5 million in the third quarter of 2016. This increase was mainly attributable to higher sales prices and higher overall operating rates. These increases were partially offset by higher feedstock and energy costs. Trading activity in the third quarter of 2017 resulted in a gain of $6.8 million as compared to a loss of $7.8 million in the third quarter of 2016.

Vinyls Segment

Net Sales. Net sales for the Vinyls segment increased by $824.9 million, or 105.5%, to $1,606.6 million in the third quarter of 2017 from $781.7 million in the third quarter of 2016. This increase was mainly attributable to higher sales contributed by Axiall and higher sales prices for our major products. Net sales for the three months ended September 30, 2017 were higher as compared to the prior-year period primarily because a full three months of Axiall's operations were included as compared to only one month of Axiall's operations included in the prior-year period. Average sales prices for the Vinyls segment increased by 18.7% in the third quarter of 2017 as compared to the third quarter of 2016. Average sales volumes for the Vinyls segment increased by 86.8% in the third quarter of 2017 as compared to the third quarter of 2016, primarily attributable to sales contributed by Axiall, as compared to the prior-year period.

Income from Operations. Income from operations for the Vinyls segment increased by $194.3 million to $216.5 million in the third quarter of 2017 from $22.2 million in the third quarter of 2016. This increase was mainly attributable to earnings contributed by Axiall and higher sales prices for our major products. These increases were partially offset by higher energy prices during the quarter ended September 30, 2017, as compared to the prior-year period.

44

Nine Months Ended September 30, 2017 Compared with Nine Months Ended September 30, 2016

Net Sales. Net sales increased by $2,690.4 million, or 80.5%, to $6,030.7 million for the nine months ended September 30, 2017 from $3,340.3 million for the nine months ended September 30, 2016, primarily attributable to higher sales contributed by Axiall, which was acquired on August 31, 2016, and higher sales prices for our major products, as compared to the nine months ended September 30, 2016. Average sales prices for the nine months ended September 30, 2017increased by 14.1% as compared to the nine months ended September 30, 2016. Overall sales volumes increased by 66.4% as compared to the nine months ended September 30, 2016, primarily attributable to sales contributed by Axiall, as compared to the prior-year period.

Gross Profit. Gross profit margin percentage increased to 21.1% for the nine months ended September 30, 2017 from 20.9% for the nine months ended September 30, 2016. The gross profit margin for the nine months ended September 30, 2017 was slightly higher primarily due to higher sales volumes for caustic soda and PVC resin contributed by Axiall and higher sales prices for our major products, as compared to the nine months ended September 30, 2016. These increases were substantially offset by a proportionately larger sales volume for the Vinyls segment as compared to the Olefins segment, Vinyls segment industry margins were lower as compared to those of the Olefins segment industry for the nine months ended September 30, 2017 and the nine months ended September 30, 2016.

Selling, General and Administrative Expenses. Selling, general and administrative expenses increased by $200.1 million to $379.9 million for the nine months ended September 30, 2017 as compared to $179.8 million in the nine months ended September 30, 2016. This increase was mainly due to selling, general and administrative expenses of Axiall which were primarily comprised of the amortization of intangible assets acquired on acquisition.

Transaction and Integration-related Costs. Transaction and integration-related costs were $22.9 million for the nine months ended September 30, 2017 as compared to $90.6 million for the nine months ended September 30, 2016. Transaction and integration-related costs were $67.7 million lower in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016 predominantly because significant transaction and integration-costs were incurred at the time of the Merger in 2016. The transaction and integration costs for the nine months ended September 30, 2017 primarily consisted of severance benefits provided to former Axiall employees in conjunction with the Merger and integration costs and consulting fees related to the Merger. The transaction and integration costs for the nine months ended September 30, 2016 primarily consisted of severance benefits provided to former Axiall executives in conjunction with the Merger, including the conversion of Axiall restricted stock units into our restricted stock units, transitional service expenses for certain former Axiall employees, retention agreement costs and consulting and professional fees related to the Merger.

Interest Expense. Interest expense increased by $81.8 million to $118.8 million for the nine months ended September 30, 2017 from $37.0 million for the nine months ended September 30, 2016 primarily as a result of higher average debt outstanding for the period as well as decreased capitalized interest on major capital projects in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016. The debt balance increased in August 2016 to finance the Merger. See "Liquidity and Capital Resources—Debt" below for further discussion on our indebtedness.

Other Income, Net. Other income, net decreased by $45.5 million to $6.6 million in the nine months ended September 30, 2017 from $52.1 million in the nine months ended September 30, 2016. The decrease was mainly attributable to the realized gain in the 2016 period of $49.1 million from the previously held common stock of Axiall.

Income Taxes. 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 nine months ended September 30, 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, 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.

45

Olefins Segment

Net Sales. Net sales for the Olefins segment increased by $111.6 million, or 7.8%, to $1,534.5 million in the nine months ended September 30, 2017 from $1,422.9 million in the nine months ended September 30, 2016, primarily due to higher sales prices for our major products. Average sales prices for the Olefins segment increased by 9.2% in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016. Average sales volumes for the Olefins segment decreased by 1.3% in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016.

Income from Operations. Income from operations for the Olefins segment increased by $80.2 million to $488.5 million in the nine months ended September 30, 2017 from $408.3 million in the nine months ended September 30, 2016. This increase was mainly attributable to higher olefins integrated product margins, primarily due to higher sales prices for our major products, higher operating rates and lower costs associated with turnarounds and outages as compared to the prior-year period. These increases were partially offset by higher energy prices. The nine months ended September 30, 2016 were negatively impacted by the planned turnaround and expansion of the Lake Charles Petro 1 ethylene unit along with other unplanned outages. Trading activity in the nine months ended September 30, 2017 resulted in a loss of $2.8 million as compared to a gain of $7.8 million in the nine months ended September 30, 2016.

Vinyls Segment

Net Sales. Net sales for the Vinyls segment increased by $2,578.8 million, or 134.5%, to $4,496.2 million in the nine months ended September 30, 2017 from $1,917.4 million in the nine months ended September 30, 2016. This increase was mainly attributable to sales contributed by Axiall and higher sales prices and volumes for our major products. The net sales for the nine months ended September 30, 2017 was higher as compared to the prior-year period primarily because nine months of Axiall's operations were included in the current period as compared to one month of Axiall operations included in the prior-year period. Average sales prices for the Vinyls segment increased by 17.8% in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016. Average sales volumes for the Vinyls segment increased by 116.7% in the nine months ended September 30, 2017 as compared to the nine months ended September 30, 2016, primarily attributable to sales contributed by Axiall, as compared to the prior-year period.

Income from Operations. Income from operations for the Vinyls segment increased by $294.7 million to $431.3 million in the nine months ended September 30, 2017 from $136.6 million in the nine months ended September 30, 2016. This increase was mainly attributable to earnings contributed by Axiall and higher sales prices and volumes for our major products. These increases were partially offset by unabsorbed fixed manufacturing costs and other costs associated with the planned turnaround and expansion at the Calvert City facility and other planned and unplanned turnarounds as well as higher energy prices during the nine months ended September 30, 2017, as compared to the prior-year period.

CASH FLOW DISCUSSION FOR THE NINE MONTHS ENDED SEPTEMBER 30, 2017 AND 2016

Cash Flows

Operating Activities

Operating activities provided cash of $962.7 million in the first nine months of 2017 compared to cash provided by operating activities of $544.2 million in the first nine months of 2016. The $418.5 millionincrease in cash flows from operating activities was mainly due to an increase in income from operations and lower turnaround related expenditures during the nine months ended September 30, 2017 as compared to the first nine months of 2016, partially offset by an increase in working capital requirements. The increase in net income from operations for the first nine months of 2017 was mainly as a result of higher sales prices and volumes, resulting in a higher margin, and earnings contributed by Axiall, which was acquired on August 31, 2016. Changes in components of working capital, which we define for purposes of this cash flow discussion as accounts receivable, net, inventories, prepaid expenses and other current assets, less accounts payable and accrued liabilities, used cash of $26.2 million in the first nine months of 2017, compared to $10.5 million of cash provided in the first nine months of 2016, an unfavorable change of $36.7 million. The change was mainly driven by an unfavorable change in accounts receivable, partially offset by favorable changes in inventory, prepaid and other current assets and accounts payable.

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Investing Activities

Net cash used for investing activities during the first nine months of 2017 was $459.4 million as compared to net cash used for investing activities of $2,389.1 million in the first nine months of 2016. In the first nine months of 2016 we used $2,437.8 million, net of cash acquired, for the acquisition of Axiall. Capital expenditures were $414.3 million in the first nine months of 2017 compared to $467.3 million in the first nine months of 2016. Capital expenditures in the first nine months of 2017 were primarily incurred on the upgrade and expansion of OpCo's Calvert City ethylene plant at our Calvert City site. Capital expenditures in the first nine months of 2016 were primarily incurred on the upgrade and expansion of OpCo's Petro 1 ethylene unit at our Lake Charles site. The remaining capital expenditures in the first nine months of 2017 and 2016 primarily related to projects to improve production capacity or reduce costs, maintenance and safety projects and environmental projects at our various facilities. In addition, we spent $47.0 million in the nine months of 2017 related to our contribution to Lotte Chemical USA Corporation to fund the construction costs of the ethylene plant. Please see "Liquidity and Capital Resources—Liquidity and Financing Arrangements" below for further discussion. Investing activities in the first nine months of 2016 included purchases of securities totaling $138.4 million. We also received aggregate proceeds of $662.9 million from the sales and maturities of our investments in the first nine months of 2016.

Financing Activities

Net cash used for financing activities during the first nine months of 2017 was $306.4 million as compared to net cash provided by financing activities of $1,560.5 million in the first nine months of 2016. We used $150.0 million and $550.0 million, respectively, for the full repayment of our term loan and the partial repayment of the Credit Agreement in the first nine months of 2017. These uses were partially offset by a drawdown under the Credit Agreement of $225.0 million in the first nine months of 2017 and net proceeds of $110.7 million from the issuance of WLKP common units as a result of its secondary offering in September 2017. During the first nine months of 2017, the restriction on $154.0 million of cash was also removed as a result of the repayment of our term loan. The remaining activities during the first nine months of 2017 were primarily related to the $76.5 million payment of cash dividends, the $20.8 million payment of cash distributions to noncontrolling interests and the $0.4 million payment of debt issuance costs. In addition, we repaid $6.7 million of Huasu's short-term notes payable to banks in connection with the payment of suppliers through letters of credit, partially offset by $5.9 million of proceeds from the issuance of such notes payable. The financing activities during the first nine months of 2016 were mainly related to the net proceeds from the issuance of our senior notes and the proceeds from our term loan of $1,428.5 in the aggregate and the drawdown under the Credit Agreement of $600.0 million, partially offset by the $125.0 million partial repayment of the Credit Agreement in the first nine months of 2016. The remaining activity during the first nine months of 2016 was primarily related to the $71.9 million payment of cash dividends, the $12.3 million payment of cash distributions to noncontrolling interests, the $35.2 million payment of debt issuance costs and the $67.4 million of cash used for repurchases of shares of our common stock. In addition, we repaid $10.6 million of Huasu's short-term notes payable to banks in connection with the payment of suppliers through letters of credit, partially offset by $5.6 million of proceeds from the issuance of such notes payable in the first nine months of 2016.

LIQUIDITY AND CAPITAL RESOURCES

Liquidity and Financing Arrangements

Our principal sources of liquidity are from cash and cash equivalents, cash from operations, short-term borrowings under the Credit Agreement and our long-term financing.

In November 2014, our Board of Directors authorized a $250.0 million share repurchase program (the "2014 Program"). In November 2015, our Board of Directors approved the expansion of the 2014 Program by an additional $150.0 million. As of September 30, 2017, we had repurchased 4,193,598 shares of our common stock for an aggregate purchase price of approximately $228.7 million under the 2014 Program. Purchases under the 2014 Program may be made either through the open market or in privately negotiated transactions. Decisions regarding the amount and the timing of purchases under the 2014 Program will be influenced by our cash on hand, our cash flow from operations, general market conditions and other factors. The 2014 Program may be discontinued by our Board of Directors at any time.

In connection with the Merger, we became 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 our vinyls facility in Lake Charles. Pursuant to the contribution and subscription agreement, we agreed to make a maximum capital commitment to LACC of up to $225.0 million 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, we had funded approximately $106.4 million of our portion of the construction costs of the ethylene plant.

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We believe that our sources of liquidity as described above will be adequate to fund our normal operations and ongoing capital expenditures. Funding of any potential large expansions or any potential acquisitions would likely necessitate and therefore depend on our ability to obtain additional financing in the future. We may not be able to access additional liquidity at cost effective interest rates due to the volatility of the commercial credit markets.

Cash and Cash Equivalents

As of September 30, 2017, our cash and cash equivalents totaled $678.2 million. In addition, we have the Credit Agreement available to supplement cash if needed, as described under "Debt" below.

Debt

As of September 30, 2017, our indebtedness, including current maturities, totaled $3.3 billion, consisting of $100.0 million of 6 ½% senior notes due 2029, $250.0 million of 6 ¾% senior notes due 2032, $89.0 million of 6 ½% senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes"), $65.0 million of 6 ½% senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes") (collectively, the "Senior Notes"), $624.8 million aggregate principal amount of 4.625% senior notes due 2021 (the "4.625% 2021 Senior Notes"), $63.2 million aggregate principal amount of the 4.625% senior notes due 2021 (the "4.625% Subsidiary 2021 Senior Notes"), $250.0 million principal amount of 3.60% senior notes due 2022 (the "3.6% senior notes due 2022"), $433.8 million aggregate principal amount of 4.875% senior notes due 2023 (the "4.875% 2023 Senior Notes"), $16.2 million aggregate principal amount of the 4.875% senior notes due 2023 (the "4.875% Subsidiary 2023 Senior Notes"), $750.0 million aggregate principal amount of 3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes"), $700.0 million aggregate principal amount of 5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes") and a $10.9 million loan from the proceeds of tax-exempt waste disposal revenue bonds (supported by an $11.3 million letter of credit), plus unamortized premium net of unamortized discount and debt issuance costs of $3.5 million. The 6 ½% senior notes due 2029, the 6 ¾% senior notes due 2032, the 6 ½% 2035 GO Zone Senior Notes and the 6 ½% 2035 IKE Zone Senior Notes evidence and secure our obligations to the Louisiana Local Government Environmental Facility and Development Authority (the "Authority"), a political subdivision of the State of Louisiana, under four loan agreements relating to the issuance of $100.0 million, $250.0 million, $89.0 million and $65.0 million aggregate principal amount of the Authority's tax-exempt revenue bonds, respectively. As of September 30, 2017, debt outstanding under the tax-exempt waste disposal revenue bonds bore interest at a variable rate. As of September 30, 2017, we were in compliance with all of the covenants with respect to the Senior Notes, the 4,625% 2021 Senior Notes, the 4.625% Subsidiary 2021 Senior Notes, the 3.60% senior notes due 2022, the 4.875% 2023 Senior Notes, the 4.875% Subsidiary 2023 Senior Notes, the 3.60% 2026 Senior Notes, the 5.0% 2046 Senior Notes, the Credit Agreement and our waste disposal revenue bonds.

Our ability to make payments on our indebtedness and to fund planned capital expenditures will depend on our ability to generate cash in the future, which is subject to general economic, financial, competitive, legislative, regulatory and other factors that are beyond our control. Based on our current level of operations and unless we were to undertake a new expansion or large acquisition, we believe our cash flow from operations, available cash and available borrowings under the Credit Agreement will be adequate to meet our normal operating needs for the foreseeable future.

Term Loan

On August 10, 2016, our indirect subsidiary, 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 $150.0 million 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 2.0% per annum, payable in arrears on the last day of each three-month period following the date of funding and at maturity.

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Credit Agreement

On August 23, 2016, we and certain of our subsidiaries entered into an unsecured revolving credit facility (the "Credit Agreement"), by and among us, the other borrowers and guarantors referred to therein, the lenders from time to time party thereto (collectively, the "Lenders"), the issuing banks party thereto and JPMorgan Chase Bank, National Association, as Administrative Agent. Under the Credit Agreement, the Lenders have committed to provide an unsecured five-year revolving credit facility in an aggregate principal amount of up to $1.0 billion. The Credit Agreement replaced our $400.0 million senior secured third amended and restated credit facility, dated as of July 17, 2014 (the "Prior ABL Credit Agreement"), by and among us, the financial institutions party thereto, as lenders, Bank of America, N.A., as agent, and us and certain of our subsidiaries, as borrowers. The Credit Agreement includes a $150.0 million sub-limit for letters of credit, and any outstanding letters of credit will be deducted from availability under the facility. The Credit Agreement also provides for a discretionary $50.0 million commitment for swing-line loans to be provided on a same-day basis. We may also increase the size of the facility, in increments of at least $25.0 million, up to a maximum of $500.0 million, subject to certain conditions and if certain Lenders agree to commit to such an increase. On October 14, 2016, certain domestic subsidiaries of Axiall and Lagoon LLC were added as subsidiary guarantors to the Credit Agreement.

At September 30, 2017, we had no borrowings outstanding under the Credit Agreement. Borrowings under the Credit Agreement will bear interest, at our option, at either (a) LIBOR plus a spread ranging from 1.0% to 1.75% that will vary depending on our credit rating or (b) Alternate Base Rate plus a spread ranging from 0.0% to 0.75% that will vary depending on our credit rating. The Credit Agreement also requires an undrawn commitment fee ranging from 0.10% to 0.25% that will vary depending on our credit rating. The Credit Agreement matures on August 23, 2021. As of September 30, 2017, we had outstanding letters of credit totaling $45.4 million and borrowing availability of $954.6 million under the Credit Agreement.

Our obligations under the Credit Agreement are guaranteed by our current and future material domestic subsidiaries, subject to customary exceptions. The Credit Agreement contains customary affirmative and negative covenants, including a quarterly total leverage ratio financial maintenance covenant. The Credit Agreement also contains customary events of default and if and for so long as an event of default has occurred and is continuing, any amounts outstanding under the Credit Agreement will accrue interest at an increased rate, the Lenders can terminate their commitments thereunder and payments of any outstanding amounts could be accelerated by the Lenders. As of September 30, 2017, we were in compliance with the total leverage ratio financial maintenance covenant.

GO Zone and IKE Zone Bonds

As of September 30, 2017, we had drawn all the proceeds from the issuance of the 6 ½% senior notes due 2029, 6 ¾% senior notes due 2032, 6 ½% 2035 GO Zone Senior Notes and 6 ½% 2035 IKE Zone Senior Notes. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources—Debt" in the 2016 Form 10-K and below for more information on the 6 ½% senior notes due 2029, the 6 ¾% senior notes due 2032, the 6 ½% 2035 GO Zone Senior Notes and the 6 ½% 2035 IKE Zone Senior Notes. All domestic restricted subsidiaries that guarantee other debt of ours or of another guarantor of the Senior Notes in excess of $5.0 million are guarantors of these notes.

The $250.0 million of 6 ¾% senior notes due November 1, 2032 under the GO Zone Act was issued by the Authority in December 2007. The bonds were subject to optional redemption by the Authority upon the direction of the Company at any time on or after November 1, 2017 for 100.0% of the principal plus accrued interest. During September 2017, we directed the Authority to optionally redeem in full $250.0 million 6 ¾% senior notes on November 1, 2017 at a redemption price of par, plus accrued and unpaid interest, if any, to the redemption date. The Authority is required to cause the GO Zone Bonds trustee to surrender the 6 ¾% senior notes due November 2032 of $250.0 million, to the Senior Notes trustee for cancellation. We used cash on hand to fund the redemption of the GO Zone Bonds.

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The indentures governing the Senior Notes contain customary covenants and events of default. Accordingly, these agreements generally impose significant operating and financial restrictions on us. These restrictions, among other things, provide limitations on incurrence of additional indebtedness, the payment of dividends, certain investments and acquisitions and sales of assets. However, the effectiveness of certain of these restrictions is currently suspended because the Senior Notes are currently rated investment grade by at least two nationally recognized credit rating agencies. The most significant of these provisions, if it were currently effective, would restrict us from incurring additional debt, except specified permitted debt (including borrowings under our credit facility), when our fixed charge coverage ratio is below 2.0:1. These limitations are subject to a number of important qualifications and exceptions, including, without limitation, an exception for the payment of our regular quarterly dividend of up to $0.10 per share. If the restrictions were currently effective, distributions in excess of $100.0 million would not be allowed unless, after giving pro forma effect to the distribution, our fixed charge coverage ratio is at least 2.0:1 and such payment, together with the aggregate amount of all other distributions after January 13, 2006, is less than the sum of 50.0% of our consolidated net income for the period from October 1, 2003 to the end of the most recent quarter for which consolidated financial statements have been filed, plus 100.0% of net cash proceeds received after October 1, 2003 as a contribution to our common equity capital or from the issuance or sale of certain securities, plus several other adjustments.

3.60% Senior Notes due 2022

The 3.60% senior notes due 2022 are unsecured and were issued with an original issue discount of $1.2 million. There is no sinking fund and no scheduled amortization of the 3.60% senior notes due 2022 prior to maturity. See "Management's Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources—Debt" in the 2016 Form 10-K for more information on the 3.60% senior notes due 2022. All of our domestic subsidiaries that guarantee other indebtedness of ours or of another guarantor of the 3.60% senior notes due 2022 in excess of $5.0 million are guarantors of the 3.60% senior notes due 2022.

The indenture governing the 3.60% senior notes due 2022 contains customary events of default and covenants that will restrict our and certain of our subsidiaries' ability to (1) incur certain secured indebtedness, (2) engage in certain sale-leaseback transactions and (3) consolidate, merge or transfer all or substantially all of our or their assets.

3.60% Senior Notes due 2026 and 5.0% Senior Notes due 2046

In August 2016, we issued $750.0 million aggregate principal amount of the 3.60% 2026 Senior Notes and $700.0 million aggregate principal amount of the 5.0% 2046 Senior Notes. In connection with the private offering and issuance of the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes, we entered into a registration rights agreement pursuant to which, among other things, we agreed to file with the SEC a registration statement relating to an offer to exchange the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes for the 2026 and 2046 Exchange Notes containing terms substantially identical to the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes (except that the transfer restrictions on the 2026 and 2046 Exchange Notes will be modified or eliminated and there will be no registration rights). On March 27, 2017, we 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 notes have been registered under 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.

All of our domestic subsidiaries that guarantee other indebtedness of ours or of another guarantor of the 3.60% 2026 Senior Notes or the 5.0% 2046 Senior Notes in excess of $40.0 million are guarantors of the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes. The indenture governing the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes contains customary events of default and covenants that will restrict our and certain of our subsidiaries' ability to (1) incur certain secured indebtedness, (2) engage in certain sale-leaseback transactions and (3) consolidate, merge or transfer all or substantially all of our or their assets. References to the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes in this paragraph refer to the 3.60% 2026 Senior Notes and the 5.0% 2046 Senior Notes that were exchanged in the exchange offers described in the preceding paragraph as well as the 3.60% 2026 Senior Notes that were not exchanged in such exchange offers.

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4.625% Senior Notes due 2021 and 4.875% Senior Notes due 2023

In September 2016, we issued $624.8 million aggregate principal amount of the 4.625% 2021 Senior Notes and $433.8 million aggregate principal amount of the 4.875% 2023 Senior Notes upon the closing of our offers to exchange any and all of the $688.0 million aggregate principal amount of the outstanding 4.625% senior notes due 2021 issued by Eagle Spinco Inc., a wholly owned subsidiary of Axiall, and the $450.0 million aggregate principal amount of the outstanding 4.875% senior notes due 2023 issued by Axiall. In connection with the private offering and issuance of the 4.625% 2021 Senior Notes and the 4.875% Senior Notes, we entered into a registration rights agreement pursuant to which, among other things, we agreed to file with the SEC a registration statement relating to an offer to exchange the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes for new SEC registered notes (the "2021 and 2023 Exchange Notes") containing terms substantially identical to the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes except that the transfer restrictions on the 2021 and 2023 Exchange Notes will be modified or eliminated and there will be no registration rights). On March 27, 2017, we commenced registered exchange offers to exchange the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes for new notes that are identical in all material respects to the 4.625% 2021 Senior Notes and the 4.875% 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 100.0% of the 4.625% 2021 Senior Notes and 100.0% of the 4.875% 2023 Senior Notes were exchanged.

All of our domestic subsidiaries that guarantee other indebtedness of ours or of another guarantor of the 4.625% 2021 Senior Notes or the 4.875% 2023 Senior Notes in excess of $40.0 million are guarantors of the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes. The indenture governing the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes contains customary events of default and covenants that will restrict our and certain of our subsidiaries' ability to (1) incur certain secured indebtedness, (2) engage in certain sale-leaseback transactions and (3) consolidate, merge or transfer all or substantially all of our or their assets. References to the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes in this paragraph refer to the 4.625% 2021 Senior Notes and the 4.875% 2023 Senior Notes that were exchanged in the exchange offers described in the preceding paragraph.

Revenue Bonds

In December 1997, we entered into a loan agreement with a public trust established for public purposes for the benefit of the Parish of Calcasieu, Louisiana. The public trust issued $10.9 million principal amount of tax-exempt waste disposal revenue bonds in order to finance our construction of waste disposal facilities for an ethylene plant. The waste disposal revenue bonds expire in December 2027 and are subject to redemption and mandatory tender for purchase prior to maturity under certain conditions. Interest on the waste disposal revenue bonds accrues at a rate determined by a remarketing agent and is payable quarterly.

Westlake Chemical Partners LP Credit Arrangements

Our subsidiary, Westlake Chemical Finance Corporation, is the lender party to a $300.0 million revolving credit facility with Westlake Chemical Partners LP ("WLKP"). On August 1, 2017, the revolving credit facility was amended to extend the maturity from 2018 to 2021. Borrowings under the revolver bear interest at LIBOR plus a spread ranging from 2.0% to 3.0% (depending on WLKP's consolidated leverage ratio), payable quarterly. WLKP may pay all or a portion of the interest on any borrowings in kind, in which case any such amounts would be added to the principal amount of the loan. As of September 30, 2017, outstanding borrowings under the credit facility totaled $253.5 million and bore interest at the LIBOR rate plus 2.0%.

Our subsidiary, Westlake Development Corporation, is the lender party to a $600.0 million revolving credit facility with OpCo. The revolving credit facility matures in 2019. As of September 30, 2017, outstanding borrowings under the credit facility totaled $223.6 million and bore interest at the LIBOR rate plus 3.0%, which is accrued in arrears quarterly.

We consolidate WLKP and OpCo for financial reporting purposes as we have a controlling financial interest. As such, the revolving credit facilities described above between our subsidiaries and WLKP and OpCo are eliminated upon consolidation.

Off-Balance Sheet Arrangements

None.

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FORWARD-LOOKING STATEMENTS

The Private Securities Litigation Reform Act of 1995 provides safe harbor provisions for forward-looking information. Certain of the statements contained in this report are forward-looking statements. All statements, other than statements of historical facts, included in this report that address activities, events or developments that we expect, project, believe or anticipate will or may occur in the future are forward-looking statements. Forward-looking statements can be identified by the use of words such as "believes," "intends," "may," "should," "could," "anticipates," "expected" or comparable terminology, or by discussions of strategies or trends. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give any assurances that these expectations will prove to be correct. Forward-looking statements relate to matters such as:

• future operating rates, margins, cash flows and demand for our products (including any changes as a result of economic growth or North American producers' competitive position);

• industry market outlook, including the price of crude oil;

• production capacities;

• currency devaluation;

• our ability to borrow additional funds under the Credit Agreement;

• our ability to meet our liquidity needs;

• our ability to meet debt obligations under our debt instruments;

• our intended quarterly dividends;

• future capacity additions and expansions in the industry;

• timing, funding and results of capital projects, such as the construction of the LACC plant and associated facilities;

• results of acquisitions, including our acquisition of Axiall (including the benefits, results and effects thereof);

• pension plan obligations, funding requirements and investment policies;

• compliance with present and future environmental regulations and costs associated with environmentally related penalties, capital expenditures, remedial actions and proceedings, including any new laws, regulations or treaties that may come into force to limit or control carbon dioxide and other greenhouse gases emissions or to address other issues of climate change;

• effects of pending legal proceedings; and

• timing of and amount of capital expenditures.

We have based these statements on assumptions and analyses in light of our experience and perception of historical trends, current conditions, expected future developments and other factors we believe were appropriate in the circumstances when the statements were made. Forward-looking statements by their nature involve substantial risks and uncertainties that could significantly impact expected results, and actual future results could differ materially from those described in such statements. While it is not possible to identify all factors, we continue to face many risks and uncertainties. Among the factors that could cause actual future results to differ materially are the risks and uncertainties discussed under "Risk Factors" in the 2016 Form 10-K and those described from time to time in our other filings with the SEC including, but not limited to, the following:

• general economic and business conditions;

• the cyclical nature of the chemical industry;

• the availability, cost and volatility of raw materials and energy;

• uncertainties associated with the United States, European and worldwide economies, including those due to political tensions and unrest in the Middle East, the Commonwealth of Independent States (including Ukraine) and elsewhere;

• current and potential governmental regulatory actions in the United States and other countries and political unrest in other areas;

• industry production capacity and operating rates;

• the supply/demand balance for our products;

• competitive products and pricing pressures;

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• instability in the credit and financial markets;

• access to capital markets;

• terrorist acts;

• operating interruptions (including leaks, explosions, fires, weather-related incidents, mechanical failure, unscheduled downtime, labor difficulties, transportation interruptions, spills and releases and other environmental risks);

• changes in laws or regulations;

• technological developments;

• our ability to realize anticipated benefits of the Merger and to integrate Axiall's business;

• charges or other liabilities relating to the Merger;

• the significant indebtedness that we have incurred in connection with the Merger;

• our ability to integrate acquired businesses other than Axiall;

• foreign currency exchange risks;

• our ability to implement our business strategies; and

• creditworthiness of our customers.

Many of such factors are beyond our ability to control or predict. Any of the factors, or a combination of these factors, could materially affect our future results of operations and the ultimate accuracy of the forward-looking statements. These forward-looking statements are not guarantees of our future performance, and our actual results and future developments may differ materially from those projected in the forward-looking statements. Management cautions against putting undue reliance on forward-looking statements or projecting any future results based on such statements or present or prior earnings levels. Every forward-looking statement speaks only as of the date of the particular statement, and we undertake no obligation to publicly update or revise any forward-looking statements.

Item 3. Quantitative and Qualitative Disclosures about Market Risk

Commodity Price Risk

A substantial portion of our products and raw materials are commodities whose prices fluctuate as market supply and demand fundamentals change. Accordingly, product margins and the level of our profitability tend to fluctuate with changes in the business cycle. We try to protect against such instability through various business strategies. Our strategies include ethylene feedstock flexibility and moving downstream into the olefins and vinyls products where pricing is more stable. We use derivative instruments in certain instances to reduce price volatility risk on feedstocks and products. Based on our open derivative positions at September 30, 2017, a hypothetical $0.10 increase in the price of a gallon of ethane would have increased our income before taxes by $6.9 million and a hypothetical $0.10 increase in the price of a gallon of propane would have increased our income before taxes by $3.8 million. Additional information concerning derivative commodity instruments appears in Notes 13 and 14 to the unaudited consolidated financial statements within this Quarterly Report on Form 10-Q.

Interest Rate Risk

We are exposed to interest rate risk with respect to fixed and variable rate debt. At September 30, 2017, we had $10.9 million principal amount of variable rate debt outstanding. The debt outstanding under the tax-exempt waste disposal revenue bonds is at a variable rate. We do not currently hedge our variable interest rate debt, but we may do so in the future. The average variable interest rate for our variable rate debt of $10.9 million as of September 30, 2017 was 1.0%. A hypothetical 100 basis point increase in the average interest rate on our variable rate debt would increase our annual interest expense by approximately $0.1 million. Also, at September 30, 2017, we had $3.3 billion aggregate principal amount of fixed rate debt. We are subject to the risk of higher interest cost if and when this debt is refinanced. If interest rates were 1.0% higher at the time of refinancing, our annual interest expense would increase by approximately $33.4 million.

Foreign Currency Exchange Rate Risk

We are exposed to foreign currency exchange rate risk associated with our international operations. However, the effect of fluctuations in foreign currency exchange rates caused by our international operations has not had a material impact on our overall operating results. We may engage in activities to mitigate our exposure to foreign currency exchange risk in certain instances through the use of currency exchange derivative instruments, including forward exchange contracts, or spot purchases. A forward exchange contract obligates us to exchange predetermined amounts of specified currencies at a stated

53

exchange rate on a stated date.

54

Item 4. Controls and Procedures

We carried out an evaluation, under the supervision and with the participation of our management, including our President and Chief Executive Officer and our Executive Vice President and Chief Financial Officer, of the effectiveness of our disclosure controls and procedures pursuant to Rules 13a-15 or 15d-15 under the Securities Exchange Act of 1934 as of the end of the period covered by this report. Based upon that evaluation, our President and Chief Executive Officer and our Executive Vice President and Chief Financial Officer concluded that our disclosure controls and procedures are effective with respect to (i) the accumulation and communication to our management, including our Chief Executive Officer and our Chief Financial Officer, of information required to be disclosed by us in the reports that we submit under the Exchange Act, and (ii) the recording, processing, summarizing and reporting of such information within the time periods specified in the SEC's rules and forms.

There were no changes in our internal control over financial reporting that occurred during the three months ended September 30, 2017 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

55

PART II. OTHER INFORMATION

Item 1. Legal Proceedings

The 2016 Form 10-K, filed on February 22, 2017, contained a description of various legal proceedings in which we are involved. See Note 18 to the unaudited consolidated financial statements within this Quarterly Report on Form 10-Q for a description of certain of those proceedings, which information is incorporated by reference herein.

Item 1A. Risk Factors

For a discussion of risk factors, please read Item 1A, "Risk Factors" in the 2016 Form 10-K. There have been no material changes from those risk factors.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

The following table provides information on our purchase of equity securities during the quarter ended September 30, 2017.

Period	Total Number of Shares Purchased (1)	Average Price Paid Per Share		Total Number of Shares Purchased as Part of Publicly Announced Plans or Programs (2)	Maximum Number (or Approximate Dollar Value) of Shares that May Yet Be Purchased Under the Plans or Programs (2)
July 2017	—	$	—	—	$	171,285,000
August 2017	—	$	—	—	$	171,285,000
September 2017	1,142	$	77.67	—	$	171,285,000
	1,142	$	77.67	—

_____________

(1) Represents shares withheld in satisfaction of withholding taxes due upon the vesting of restricted stock units granted to our employees under the 2013 Plan.

(2) In November 2014, our Board of Directors authorized a $250.0 million share repurchase program (the "2014 Program"). In November 2015, our Board of Directors approved the expansion of the 2014 Program by an additional $150.0 million. As of September 30, 2017, 4,193,598 shares of common stock had been acquired at an aggregate purchase price of approximately $228.7 million under the 2014 Program. Transaction fees and commissions are not reported in the average price paid per share in the table above. Decisions regarding the amount and the timing of purchases under the 2014 Program will be influenced by our cash on hand, our cash flow from operations, general market conditions and other factors. The 2014 Program may be discontinued by our Board of Directors at any time.

56

Item 6. Exhibits

Exhibit No.	EXHIBIT INDEX
10.1†	Investment Management Agreement among Westlake Chemical Corporation, Westlake Chemical OpCo LP and Westlake Chemical Partners LP, dated as of August 1, 2017
31.1†	Rule 13a – 14(a) / 15d – 14(a) Certification (Principal Executive Officer)
31.2†	Rule 13a – 14(a) / 15d – 14(a) Certification (Principal Financial Officer)
32.1#	Section 1350 Certification (Principal Executive Officer and Principal Financial Officer)
101.INS†	XBRL Instance Document
101.SCH†	XBRL Taxonomy Extension Schema Document
101.CAL†	XBRL Taxonomy Extension Calculation Linkbase Document
101.DEF†	XBRL Taxonomy Extension Definition Linkbase Document
101.LAB†	XBRL Taxonomy Extension Label Linkbase Document
101.PRE†	XBRL Taxonomy Extension Presentation Linkbase Document

______________________________

† Filed herewith.

# Furnished herewith.

57

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		WESTLAKE CHEMICAL CORPORATION
Date:	November 7, 2017	By:	/S/    ALBERT CHAO
			Albert Chao
			President and Chief Executive Officer (Principal Executive Officer)
Date:	November 7, 2017	By:	/S/    M. STEVEN BENDER
			M. Steven Bender
			Executive Vice President and Chief Financial Officer (Principal Financial Officer)

58

EX-10.1

Exhibit 10.1

INVESTMENT MANAGEMENT AGREEMENT

among

WESTLAKE CHEMICAL CORPORATION,

WESTLAKE CHEMICAL OPCO LP,

and

WESTLAKE CHEMICAL PARTNERS LP

Dated as of August 1, 2017

INVESTMENT MANAGEMENT AGREEMENT

This INVESTMENT MANAGEMENT AGREEMENT (this “Agreement”) is made as of August 1, 2017, among WESTLAKE CHEMICAL CORPORATION, a Delaware corporation (“Westlake”), WESTLAKE CHEMICAL OPCO LP, a Delaware limited partnership (“OpCo”), and WESTLAKE CHEMICAL PARTNERS LP, a Delaware limited partnership (“MLP”).

WITNESSETH:

WHEREAS, OpCo and MLP from time to time have the need to make short-term investments of surplus cash; and

WHEREAS, OpCo and MLP expect to access more diverse range of investment options on the investment of surplus cash through joint investment with Westlake and its affiliates; and

WHEREAS, the parties have determined that it is therefore advisable and in the best interests of OpCo and MLP to authorize Westlake to establish, maintain and manage a cash and investment management system for excess cash and investments of OpCo and MLP, including authorizing Westlake to hold in Westlake’s own accounts to manage OpCo’s and MLP’s cash and investments; and

NOW, THEREFORE, in consideration of the mutual promises contained herein, the parties hereto agree as follows:

1.Investment Manager. OpCo and MLP hereby appoint Westlake as their agent with the power and discretion to act as investment manager (the “Investment Manager”) with respect to their excess cash, and direct the Investment Manager to invest such excess cash for the duration(s) either of them may specify from time to time.

2.Duties, Authority and Covenants.

(a)The Investment Manager will have the authority, as agent for and in the name of OpCo and MLP, to make investment decisions, to arrange for the executions of purchases and sales, and generally to manage the investment of the excess cash of OpCo and MLP on a fully discretionary basis (subject to compliance with the Investment Guidelines referred to in Section 3(a) below).

(b)All funds and other assets comprising the investments of OpCo and MLP, (the “Portfolios”) shall be held in the name of the Investment Manager either directly by the

Investment Manager or by appropriate banks, trust companies, brokers, dealers or other custodians (each a “Custodian”), and all payments in respect of investment transactions shall be handled directly between the Investment Manager and its respective Custodians. OpCo and MLP consent to the commingling of the Portfolios with funds and other assets comprising investments of the Investment Manager and its other direct and indirect subsidiaries.

(c)In the event that either OpCo or MLP requests any cash from its Portfolio earlier than the duration(s) specified in Section 1 above, the Investment Manager may liquidate the necessary portion of the Portfolio in a prudent and efficient manner to minimize any loss of capital and investment income complying with such request and transfer the requested cash to the order of OpCo or MLP, as the case may be. Notwithstanding any of the foregoing, OpCo and MLP shall receive the Earnings as calculated in Section 3(c) below.

3.Investment Guidelines, Fees, Costs and Income.

(a)Investment Guidelines. The Investment Manager shall adhere to the Investment Guidelines attached hereto as “Annex A” when investing excess cash on behalf of OpCo or MLP.

(b)OpCo and MLP shall each reimburse the Investment Manager for their allocable shares of any fees and expenses paid by the Investment Manager with respect to managing their respective Portfolios, including, but not limited to costs of consultants and other professionals, whether related or unrelated to the Investment Manager.

(c)The Investment Manager shall pay each of OpCo and MLP based on the sum of (a) the then applicable interest curve for A2/P2 US-dollar denominated commercial paper as published by Bloomberg and (b) five basis point, multiplied by the total balance of their respective Portfolio for any applicable one-day, one-week, one-month, three-month, six-month or nine-month duration (“Earnings”). A sample screen shot of the interest curve is attached hereto as “Annex B”.

4.No Joint Venture, etc. The parties hereto acknowledge that this Agreement shall not create and shall not be construed to create a relationship of joint tenancy, joint venturers, co-partners, employer and employee, master and servant or any similar relationship between the parties hereto.

5.Exculpation; Indemnification.

(a)None of Westlake, its affiliates or any of their respective members, managers, partners, directors, officers and employees and the legal representatives of any of them (each, an “IndemnifiedAffiliate”) shall be liable to OpCo, Westlake Chemical OpCo GP LLC, Westlake

2

Chemical Partners LP or Westlake Chemical Partners GP LLC, for any mistakes of judgment or acts or omissions arising out of or in connection with any investment made or held by OpCo and MLP, as the case maybe, hereunder or this Agreement except in the case of a liability resulting from Westlake’s or such Indemnified Affiliate’s own fraud, gross negligence, willful misconduct or bad faith. Each Indemnified Affiliate may consult with counsel and accountants in respect of OpCo’s and MLP’s affairs and be fully protected and justified in any action or inaction that is taken in accordance with the advice or opinion of such counsel and accountants.

(b)To the fullest extent permitted by law, OpCo and MLP shall indemnify and hold harmless Westlake and its Indemnified Affiliates (each, an “IM Indemnitee”), against any loss, cost or expense suffered or sustained by an IM Indemnitee by reason of any acts, omissions or alleged acts or omissions arising out of, or in connection with OpCo and MLP, as the case may be, any investment made or held by OpCo and MLP, as the case may be, or this Agreement, including, without limitation, any judgment, award, settlement, reasonable attorneys’ fees and other costs or expenses incurred in connection with the defense of any actual or threatened action, proceeding, or claim, provided that such acts, omissions or alleged acts or omissions upon which such actual or threatened action, proceeding or claim are based were not made in bad faith or did not constitute fraud, willful misconduct or gross negligence by such IM Indemnitee. Each of OpCo and MLP shall, in the sole discretion of Westlake, advance to any IM Indemnitee reasonable attorneys’ fees and other costs and expenses incurred in connection with the defense of any action or proceeding that arises out of such conduct. In the event that any advance described in the preceding sentence is made by OpCo and MLP, the IM Indemnitee receiving such advance shall agree to reimburse OpCo and MLP for such fees, costs and expenses to the extent that it shall be determined that it was not entitled to indemnification under this Agreement.

(c)The provisions of this Section 6 shall survive any termination of this Agreement.

6.Term and Termination.

(a)This Agreement shall terminate upon the termination date set forth in a notice of termination delivered by the Investment Manager to OpCo and MLP, as the case may be, or by OpCo and MLP, as the case may be, to the Investment Manager, not less than 30 days prior to the termination date set forth therein.

(b)Upon any such termination of this Agreement, OpCo or MLP, as the case may be, shall pay the Investment Manager (i) all fees and expenses that have been incurred by the Investment Manager prior to the date of such termination and to the extent reimbursable under

3

Section 4(b), and (ii) any fees and expenses that have accrued to the Investment Manager as of the date of such termination.

(c)Upon any such termination of this Agreement, Westlake shall cause to be paid to OpCo or MLP, as the case may be, (i) OpCo’s or MLP’s Earnings, if any, and (ii) OpCo’s or MLP’s respective Portfolio.

7.Miscellaneous.

(a)Notices. All notices, reports and other communications given pursuant to this Agreement shall be in writing and shall be (i) sent by e-mail or (ii) accomplished by any other method agreed upon by the parties hereto in writing. Notice given in any other manner shall be effective when received by the addressee or its agent.

(b)Assignment. This Agreement shall be binding upon and inure to the benefit of the parties and their respective successors and permitted assigns. No party to this Agreement may assign or delegate its rights or duties under this Agreement, except to the extent expressly provided herein, without the consent of the other parties hereto.

(c)Amendment; Waiver. Except as otherwise provided herein, this Agreement may not be amended except by a written instrument signed by the parties hereto. Neither the failure nor delay on the part of any party hereto to exercise any right, remedy, power or privilege under this Agreement shall operate as a waiver thereof. No waiver shall be effective unless it is in writing and is signed by the party asserted to have granted such waiver.

(d)Severability. Any provision of this Agreement which is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction only, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction.

(e)Entire Agreement. This Agreement constitutes the entire agreement between the parties hereto with respect to the subject matter hereof and supersedes any prior agreement or understanding between them with respect to such subject matter.

(f)Reliance by Third Parties. The signatures of Westlake shall be sufficient to bind OpCo and MLP, as the case may be, with respect to matters provided for under this Agreement.

4

(g)Governing Law. This Agreement shall be governed by and construed in accordance with the laws of the State of Texas, without regard for the principles of conflict of laws thereof.

(h)Jurisdiction; Consent to Service of Process. With respect to any judicial proceeding involving any dispute, controversy or claim arising out of or relating to this Agreement, each of the parties hereto irrevocably and unconditionally agrees (i) to be subject to the jurisdiction of the courts of the State of Texas and of the United States District Court for the Southern District of Texas, and any courts appealable from any such courts, (ii) that, to the fullest extent permitted by applicable law, service of process may be made on any party hereto by prepaid certified mail with a validated proof of mailing receipt constituting evidence of valid service and (iii) that service made pursuant to the immediately preceding clause (ii) shall, to the fullest extent permitted by applicable law, have the same legal force and effect as if served upon such party personally within the State of Texas.

5

IN WITNESS WHEREOF the parties hereto, by their duly authorized representatives, have executed this Agreement as of the day and year first written above.

WESTLAKE CHEMICAL CORPORATION

By: /S/ M. STEVEN BENDER   Name: M. Steven Bender
   Title: Executive Vice President &

                       Chief Financial Officer

WESTLAKE CHEMICAL OPCO LP

By: Westlake Chemical OpCo GP LLC, its general partner

By: /S/ M. STEVEN BENDER   Name: M. Steven Bender
   Title:  Executive Vice President &

                       Chief Financial Officer

WESTLAKE CHEMICAL PARTNERS LP

By: Westlake Chemical Partners GP LLC, its general partner

By: /S/ M. STEVEN BENDER   Name: M. Steven Bender
   Title: Executive Vice President &

                       Chief Financial Officer

Annex A

Investment Guidelines

Westlake Chemical Corporation

Corporate Investment Policy Summary

This Corporate Cash Investing Policy shall limit investment activities of Westlake Chemical Corporation (WCC) in order to insure safety, liquidity, and preservation of capital.

Summary of Policies:

a) WCC shall restrict its cash investments to maturities less than 366 days from the date of settlement. The average weighted maturity shall be consistent with the cash needs of the corporation as determined by its cash forecast.

b) WCC shall restrict its excess cash to the following categories of investments:

i) Direct obligations of the United States of America, or any agency thereof, or obligations guaranteed as to principal and interest by the United States of America, maturing not more than one year from the date of acquisition thereof;

ii) Domestic certificates of deposit and banker’s acceptances issued by any bank or trust company organized under the laws of the United States of America or any state thereof and having: surplus and undivided profits of at least $500,000,000, an individual rating from Fitch of B/C or better, and maturing not more than one year from the date of acquisition thereof.

iii) Time deposits, Eurodollar and Yankee certificates of deposit issued by any bank having capital, surplus, and undivided profits of at least $500,000,000 and short term ratings of A-2 (S&P) or P-2 (Moody’s) or better, maturing not more than six months from the date of acquisition thereof.

iv) Commercial paper rated A-2 (S&P) or P-2 (Moody’s) or better, maturing not more than 120 days from the date of acquisition thereof, and

v) Dollar denominated money market funds as approved by management.

c) WCC shall at no time borrow funds from any institution in order to use such funds for speculative purposes.

d) WCC will diversify external cash investments consistent with liquidity, safety, and preservation of capital.

e) This investment policy may be changed or modified, as required, by the WCC CFO.

Approved by:

/S/ JEFF HOLYJeff Holy

Treasurer

August 1, 2017

Annex B

A2/P2 Commercial Paper interest curve

EX-31.1

Exhibit 31.1

CERTIFICATIONS

I, Albert Chao, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of Westlake Chemical Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

a) all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

b) any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date:	November 7, 2017	/S/    ALBERT CHAO
		Albert Chao
		President and Chief Executive Officer (Principal Executive Officer)

EX-31.2

Exhibit 31.2

CERTIFICATIONS

I, M. Steven Bender, certify that:

1. I have reviewed this Quarterly Report on Form 10-Q of Westlake Chemical Corporation;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

a) all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

b) any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date:	November 7, 2017	/S/ M. STEVEN BENDER
		M. Steven Bender
		Executive Vice President and Chief Financial Officer (Principal Financial Officer)

EX-32.1

Exhibit 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. SECTION 1350

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Westlake Chemical Corporation (the "Company") on Form 10-Q for the fiscal quarter ended September 30, 2017 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), I, Albert Chao, President and Chief Executive Officer of the Company, and I, M. Steven Bender, Executive Vice President and Chief Financial Officer of the Company, certify, to the best of our knowledge, pursuant to 18 U.S.C. §1350, as adopted pursuant to §906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material aspects, the financial condition and results of operations of the Company.

Date:	November 7, 2017	/S/    ALBERT CHAO
		Albert Chao
		President and Chief Executive Officer (Principal Executive Officer)
Date:	November 7, 2017	/S/    M. STEVEN BENDER
		M. Steven Bender
		Executive Vice President and Chief Financial Officer (Principal Financial Officer)

XML

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	2017
Document Fiscal Period Focus	Q3
Trading Symbol	WLK
Entity Registrant Name	WESTLAKE CHEMICAL CORP
Entity Central Index Key	0001262823
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		129,107,447

XML

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

XML

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

XML

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

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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

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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

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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

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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.

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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.

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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		)

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Accounts Receivable

9 Months Ended

Sep. 30, 2017

Accounts Receivable, Net [Abstract]

Accounts Receivable

Accounts Receivable

Accounts receivable consist of the following:

	September 30, 2017			December 31, 2016
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

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Inventories

9 Months Ended

Sep. 30, 2017

Inventory Disclosure [Abstract]

Inventories

Inventories

Inventories consist of the following:

	September 30, 2017		December 31, 2016
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

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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.

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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.

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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.

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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 Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt		Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt
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.

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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. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans
Service cost	$	1,336		$	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. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans
Service cost	$	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

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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.

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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.

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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 arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	4,336			4,336		—
	4,336			4,336		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(704		)	—		(704		)
	(704		)	—		(704		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(1,410		)	745		(2,155		)
Derivative positions not subject to enforceable master netting arrangements	(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 arrangements	$	1,498		$	1,636	$	(138	)
Derivative positions not subject to enforceable master netting arrangements	6,091			6,091		—
	7,589			7,727		(138		)
Deferred charges and other assets, net
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	5,249			5,249		—
	5,249			5,249		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(1,349		)	—		(1,349		)
	(1,349		)	—		(1,349		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(436		)	2,010		(2,446		)
Derivative positions not subject to enforceable master netting arrangements	(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.

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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

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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.

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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.

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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

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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.

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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, 2017		December 31, 2016
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

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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.

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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.

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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

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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.

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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.

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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		)

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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, 2017			December 31, 2016
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

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Inventories (Tables)

9 Months Ended

Sep. 30, 2017

Inventory Disclosure [Abstract]

Schedule Of Inventory

Inventories consist of the following:

	September 30, 2017		December 31, 2016
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

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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

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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 Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt		Principal Amount		Unamortized Premium, Discount and Debt Issuance Costs			Net Long-term Debt
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

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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. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans		U.S. Plans		Non-U.S. Plans
Service cost	$	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. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans			U.S. Plans			Non-U.S. Plans
Service cost	$	1,336		$	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

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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.

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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 arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	4,336			4,336		—
	4,336			4,336		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(704		)	—		(704		)
	(704		)	—		(704		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(1,410		)	745		(2,155		)
Derivative positions not subject to enforceable master netting arrangements	(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 arrangements	$	1,498		$	1,636	$	(138	)
Derivative positions not subject to enforceable master netting arrangements	6,091			6,091		—
	7,589			7,727		(138		)
Deferred charges and other assets, net
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	5,249			5,249		—
	5,249			5,249		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(1,349		)	—		(1,349		)
	(1,349		)	—		(1,349		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(436		)	2,010		(2,446		)
Derivative positions not subject to enforceable master netting arrangements	(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

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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

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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

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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

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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, 2017		December 31, 2016
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

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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

XML

Acquisition (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions			3 Months Ended		9 Months Ended
	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	$ 33.00
Purchase consideration	$ 2,539,360

XML

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)		$ 2.00
Axiall Corporation [Member]
Business Acquisition, Pro Forma Information [Line Items]
Divestitures	$ 26,666
Restructuring costs	22,881
Legal and settlement claims, net	$ 23,376

XML

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)	$ 33.00
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

XML

Acquisition (Purchase Price Allocation) (Details) - USD ($) $ in Thousands		9 Months Ended
	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)

XML

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

XML

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)

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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

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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

XML

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

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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

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Other Assets (Changes in Goodwill) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
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

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Term Loan (Narrative) (Details) - Line of Credit [Member] - Term Loan Facility Maturing March 31, 2017 [Member] $ in Thousands	Aug. 10, 2016 USD ($)
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%

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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	2021
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	2021
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	2022
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	2023
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	2023
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	2026
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	2027
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	2029
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	2032
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	2035
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	2035
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	2046
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

XML

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%

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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%

XML

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%

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

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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

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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

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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

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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

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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

XML

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)					$ 33.00

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Derivative Instruments (Narrative) (Details) - Not Designated as Hedging Instrument [Member] - Commodity Forward Contracts [Member]	9 Months Ended	12 Months Ended
	Sep. 30, 2017 MMBTU gal	Dec. 31, 2016 MMBTU gal
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

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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

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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

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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

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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	2021
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	2021
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	2022
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	2023
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	2023
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	2026
Stated interest rate (percent)	3.60%
Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2027
6 1/2% Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2029
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	2032
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	2035
Stated interest rate (percent)	6.50%
2035 IKE Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt Instrument Maturity	2046
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

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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%

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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

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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

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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

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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

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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

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Commitments and Contingencies (Additional Information) (Detail) $ in Thousands	1 Months Ended	9 Months Ended	12 Months Ended
	Oct. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) settlement	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2016 USD ($)	Jun. 17, 2015 USD ($)
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

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

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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

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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

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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

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Westlake Chemical Partners Offerings (Details) - USD ($) $ / shares in Units, $ in Thousands				9 Months Ended
	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	$ 22.00		$ 24.00
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%

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Guarantor Disclosures (Additional Information) (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($)
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	2022
3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2026
5% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2046
4.625% Senior Notes Due 2021 (New Westlake 2021 Notes) [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2021
4.875% Senior Notes Due 2023 (New Westlake 2023 Notes) [Member] | Senior Notes [Member]
Condensed Financial Statements, Captions [Line Items]
Debt Instrument Maturity	2023

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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

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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

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Guarantor Disclosures (Condensed Consolidating Financial Information Statement of Cash Flows) (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	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