Westlake (WLK) 10-Q 6 Aug 19 2019 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2019
Entity File Number	001-32260
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Entity Registrant Name	Westlake Chemical Corporation
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0346924
Entity Address, Address Line One	2801 Post Oak Boulevard
Entity Address, Address Line Two	Suite 600
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77056
City Area Code	713
Local Phone Number	960-9111
Title of 12(b) Security	Common Stock
Trading Symbol	WLK
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		128,268,740
Entity Central Index Key	0001262823
Current Fiscal Year End Date	--12-31
Amendment Flag	false

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 409	$ 753
Accounts receivable, net	1,213	1,037
Inventories	925	1,014
Prepaid expenses and other current assets	48	38
Total current assets	2,595	2,842
Property, plant and equipment, net	6,832	6,595
Operating lease right-of-use assets	381	0
Goodwill	1,079	1,002
Customer relationships, net	559	525
Other intangible assets, net	204	134
Other assets, net	566	504
Total assets	12,216	11,602
Current liabilities
Accounts and notes payable	521	507
Accrued and other liabilities	733	676
Total current liabilities	1,254	1,183
Long-term debt, net	2,669	2,668
Deferred income taxes	1,206	1,159
Pension and other post-retirement benefits	334	337
Operating lease liabilities	294	0
Other liabilities	200	179
Total liabilities	5,957	5,526
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 June 30, 2019 and December 31, 2018, respectively	1	1
Common stock, held in treasury, at cost; 6,382,640 and 6,183,125 shares at June 30, 2019 and December 31, 2018, respectively	(390)	(382)
Additional paid-in capital	558	556
Retained earnings	5,600	5,477
Accumulated other comprehensive loss	(50)	(62)
Total Westlake Chemical Corporation stockholders' equity	5,719	5,590
Noncontrolling interests	540	486
Total equity	6,259	6,076
Total liabilities and equity	$ 12,216	$ 11,602

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Preferred stock, par value, in dollars per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, in dollars per share	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common Stock [Member]
Common Stock, Shares, Issued	134,651,380	134,651,380
Common Stock, Held in Treasury [Member]
Treasury Stock, Shares	6,382,640	6,183,125

Consolidated Statements of Oper

Consolidated Statements of Operations (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 2,144	$ 2,235	$ 4,169	$ 4,385
Cost of sales	1,804	1,683	3,530	3,291
Gross profit	340	552	639	1,094
Selling, general and administrative expenses	117	115	233	223
Amortization of intangibles	27	25	54	51
Restructuring, transaction and integration-related costs	2	8	24	15
Income from operations	194	404	328	805
Other income (expense)
Interest expense	(28)	(31)	(58)	(68)
Other income, net	2	8	11	30
Income before income taxes	168	381	281	767
Provision for income taxes	39	93	70	182
Net income	129	288	211	585
Net income attributable to noncontrolling interests	10	10	20	20
Net income attributable to Westlake Chemical Corporation	$ 119	$ 278	$ 191	$ 565
Earnings per common share attributable to Westlake Chemical Corporation:
Basic (in dollars per share)	$ 0.92	$ 2.13	$ 1.48	$ 4.34
Diluted (in dollars per share)	$ 0.92	$ 2.12	$ 1.47	$ 4.31
Weighted average common shares outstanding:
Basic (in shares)	128,485,182	129,624,291	128,506,712	129,554,528
Diluted (in shares)	128,850,335	130,306,615	128,881,952	130,249,084

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 129	$ 288	$ 211	$ 585
Foreign Currency Translation Adjustment, by Component [Abstract]
Foreign currency translation	15	(37)	13	(43)
Income tax benefit (provision) on foreign currency translation	(2)	(3)	(2)	1
Other comprehensive income (loss), net of income taxes	13	(40)	11	(42)
Comprehensive income	142	248	222	543
Comprehensive income attributable to noncontrolling interests, net of tax of $0 and $1 for the three months ended June 30, 2019 and 2018; and net of tax of $1 and $2 for the six months ended June 30, 2019 and 2018, respectively	9	6	19	18
Comprehensive income attributable to Westlake Chemical Corporation	$ 133	$ 242	$ 203	$ 525

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Income (Unaudited) OCI Parenthetical - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
OCI Parenthetical [Abstract]
Other Comprehensive Income (Loss), Tax, Portion Attributable to Noncontrolling Interest	$ 0	$ 1	$ 1	$ 2

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Stockholders' Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Common Stock, Held in Treasury [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 1				$ 1
Beginning balances at Dec. 31, 2017	5,369	$ 1	$ (302)	$ 555	4,613	$ 7	$ 495
Beginning balance, shares issued at Dec. 31, 2017		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2017			5,232,875
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation					287
Net income attributable to noncontrolling interests							10
Net income	297
Other comprehensive income (loss)	(2)					(4)	2
Shares issued—stock- based compensation (in shares)			(175,143)
Shares issued—stock-based compensation	6		$ 10	(4)	0
Stock-based compensation	4			4
Dividends declared	(27)				(27)
Distributions to noncontrolling interests	(7)						(7)
Ending balances at Mar. 31, 2018	5,641	$ 1	$ (292)	555	4,874	3	500
Ending balance, shares issued at Mar. 31, 2018		134,651,380
Ending balance, Treasury shares at Mar. 31, 2018			5,057,732
Beginning balances at Dec. 31, 2017	5,369	$ 1	$ (302)	555	4,613	7	495
Beginning balance, shares issued at Dec. 31, 2017		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2017			5,232,875
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	565
Net income attributable to noncontrolling interests	20
Net income	585
Other comprehensive income (loss)	(42)
Ending balances at Jun. 30, 2018	5,846	$ 1	$ (289)	558	5,125	(33)	484
Ending balance, shares issued at Jun. 30, 2018		134,651,380
Ending balance, Treasury shares at Jun. 30, 2018			4,999,765
Beginning balances at Mar. 31, 2018	5,641	$ 1	$ (292)	555	4,874	3	500
Beginning balance, shares issued at Mar. 31, 2018		134,651,380
Beginning balance, Treasury shares at Mar. 31, 2018			5,057,732
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	278				278
Net income attributable to noncontrolling interests	10						10
Net income	288
Other comprehensive income (loss)	(40)					(36)	(4)
Shares issued—stock- based compensation (in shares)			(57,967)
Shares issued—stock-based compensation	2		$ 3	(1)	0
Stock-based compensation	4			4
Dividends declared	(27)				(27)
Distributions to noncontrolling interests	(22)						(22)
Ending balances at Jun. 30, 2018	5,846	$ 1	$ (289)	558	5,125	(33)	484
Ending balance, shares issued at Jun. 30, 2018		134,651,380
Ending balance, Treasury shares at Jun. 30, 2018			4,999,765
Beginning balances at Dec. 31, 2018	6,076	$ 1	$ (382)	556	5,477	(62)	486
Beginning balance, shares issued at Dec. 31, 2018		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2018			6,183,125
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation					72
Net income attributable to noncontrolling interests							10
Net income	82
Other comprehensive income (loss)	(2)					(2)	0
Shares issued—stock- based compensation (in shares)			(124,052)
Shares issued—stock-based compensation	0		$ 11	(8)	(3)
Stock-based compensation	7			7
Dividends declared	(33)				(33)
Distributions to noncontrolling interests	(8)						(8)
Issuance of Westlake Chemical Partners LP common units	63			(2)			65
Ending balances at Mar. 31, 2019	6,185	$ 1	$ (371)	553	5,513	(64)	553
Ending balance, shares issued at Mar. 31, 2019		134,651,380
Ending balance, Treasury shares at Mar. 31, 2019			6,059,073
Beginning balances at Dec. 31, 2018	6,076	$ 1	$ (382)	556	5,477	(62)	486
Beginning balance, shares issued at Dec. 31, 2018		134,651,380
Beginning balance, Treasury shares at Dec. 31, 2018			6,183,125
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	191
Net income attributable to noncontrolling interests	20
Net income	211
Other comprehensive income (loss)	11
Ending balances at Jun. 30, 2019	6,259	$ 1	$ (390)	558	5,600	(50)	540
Ending balance, shares issued at Jun. 30, 2019		134,651,380
Ending balance, Treasury shares at Jun. 30, 2019			6,382,640
Beginning balances at Mar. 31, 2019	6,185	$ 1	$ (371)	553	5,513	(64)	553
Beginning balance, shares issued at Mar. 31, 2019		134,651,380
Beginning balance, Treasury shares at Mar. 31, 2019			6,059,073
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Westlake Chemical Corporation	119				119
Net income attributable to noncontrolling interests	10						10
Net income	129
Other comprehensive income (loss)	13					14	(1)
Common stock repurchased, shares			342,740
Common stock, repurchased	(20)		$ (20)
Shares issued—stock- based compensation (in shares)			(19,173)
Shares issued—stock-based compensation	0		$ 1	(1)	0
Stock-based compensation	6			6
Dividends declared	(32)				(32)
Distributions to noncontrolling interests	(22)						(22)
Ending balances at Jun. 30, 2019	$ 6,259	$ 1	$ (390)	$ 558	$ 5,600	$ (50)	$ 540
Ending balance, shares issued at Jun. 30, 2019		134,651,380
Ending balance, Treasury shares at Jun. 30, 2019			6,382,640

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 211	$ 585
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	347	312
Stock-based compensation expense	13	11
Disposition and write-off of property, plant and equipment	27	15
Deferred income taxes	15	45
Other losses, net	16	0
Changes in operating assets and liabilities
Accounts receivable	(119)	(272)
Inventories	125	(9)
Prepaid expenses and other current assets	(8)	(13)
Accounts payable	(40)	(11)
Accrued and other liabilities	(62)	(70)
Other, net	(58)	(44)
Net cash provided by operating activities	467	549
Cash flows from investing activities
Acquisition of businesses, net of cash acquired	(314)	0
Additions to property, plant and equipment	(411)	(312)
Additions to investments in unconsolidated subsidiaries	(42)	(45)
Other, net	4	3
Net cash used for investing activities	(763)	(354)
Cash flows from financing activities
Dividends paid	(65)	(54)
Distributions to noncontrolling interests	(30)	(29)
Proceeds from notes payable	7	6
Proceeds from issuance of Westlake Chemical Partners LP common units	63	0
Redemption and repayment of notes payable	(5)	(1,173)
Repurchase of common stock for treasury	(20)	0
Other	2	8
Net cash used for financing activities	(48)	(1,242)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0	(2)
Net decrease in cash, cash equivalents and restricted cash	(344)	(1,049)
Cash, cash equivalents and restricted cash at beginning of period	775	1,554
Cash, cash equivalents and restricted cash at end of period	$ 431	$ 505

Basis of Financial Statements (

Basis of Financial Statements (Notes)	6 Months Ended
	Jun. 30, 2019
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 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, 2018 (the " 2018 Form 10-K"), filed with the SEC on February 20, 2019 . 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, 2018 with the exception of those accounting standards adopted in 2019 as discussed in Note 1. In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of June 30, 2019 , its results of operations for the three and six months ended June 30, 2019 and 2018 , and the changes in its cash position for the six months ended June 30, 2019 and 2018 . 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, 2019 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 Credit Losses (ASU No. 2016-13) In June 2016, the Financial Accounting Standards Board ("FASB") issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Fair Value Measurement (ASU No. 2018-13) In August 2018, the FASB issued an accounting standards update to modify the disclosure requirements on fair value measurements. The amendments are effective for periods beginning after December 15, 2019. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until the effective date. Most amendments should be applied retrospectively, but certain amendments will be applied prospectively. The Company is in the process of assessing the impact of the standard on the Company's fair value disclosures. However, the standard is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standards Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on lease accounting that supersedes the previously issued leases guidance. The new standard requires lessees to recognize assets and liabilities for all long-term operating leases. An asset is recognized for the right to use an underlying leased asset and a liability is recognized for the obligation to make payments over the lease term. The standard also requires expanded lease disclosures. The standard requires a modified retrospective adoption approach and allows for the election of certain transition expedients. The Company adopted the standard January 1, 2019 using the optional transition method which allows entities to recognize a cumulative adjustment to the opening balance sheet in the period of adoption. The Company elected the package of optional transition expedients and was not required to reassess (1) whether any existing contracts are or contain leases, (2) classification of existing leases as operating or capital or (3) whether initial direct costs for existing leases qualify for capitalization under the new accounting standard. The Company did not elect the use of hindsight to determine the lease term when considering lease renewal or termination options. Additionally, the Company elected to continue accounting for existing land easements under its accounting policies that were in effect prior to adoption of the new lease standard. The following amounts were recorded as a result of adopting the new lease standard on January 1, 2019: Operating Lease Assets and Liabilities Balance Sheet Location Amounts Recorded in the Consolidated Balance Sheet January 1, 2019 Right-of-use assets Operating lease right-of-use assets $ 421 Current lease liabilities Accrued and other liabilities (94 ) Non-current lease liabilities Operating lease liabilities (331 ) Deferred rent Other liabilities 4

Financial Instruments (Notes)

Financial Instruments (Notes)	6 Months Ended
	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments Cash Equivalents The Company had $50 and $10 of held-to-maturity securities with original maturities of three months or less, primarily consisting of corporate debt securities, classified as cash equivalents at June 30, 2019 and December 31, 2018 , respectively. The Company's investments in held-to-maturity securities were held at amortized cost, which approximates fair value. Restricted Cash and Cash Equivalents The Company had restricted cash and cash equivalents of $22 and $22 at June 30, 2019 and December 31, 2018 . The Company's restricted cash and cash equivalents are related to balances that are restricted for payment of distributions to certain of the Company's current and former employees and are reflected primarily in other assets, net in the consolidated balance sheets.

Accounts Receivable (Notes)

Accounts Receivable (Notes)	6 Months Ended
	Jun. 30, 2019
Accounts Receivable, Net [Abstract]
Accounts Receivable	Accounts Receivable Accounts receivable consist of the following: June 30, December 31, Trade customers $ 1,152 $ 969 Related parties 8 6 Allowance for doubtful accounts (24 ) (23 ) 1,136 952 Federal and state taxes 51 57 Other 26 28 Accounts receivable, net $ 1,213 $ 1,037

Inventories (Notes)

Inventories (Notes)	6 Months Ended
	Jun. 30, 2019
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of the following: June 30, December 31, Finished products $ 558 $ 657 Feedstock, additives, chemicals and other raw materials 212 203 Materials and supplies 155 154 Inventories $ 925 $ 1,014

Leases (Notes)

Leases (Notes)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases The Company is obligated under various long-term and short-term operating leases for rail cars, buildings, land and other transportation and storage assets. The Company determines whether an arrangement is, or contains, a lease at contract inception. Some of the Company's arrangements contain both lease and non-lease components. For certain transportation equipment leases, the Company accounts for the lease and non-lease components as a single lease component. The Company records right-of-use assets and corresponding lease liabilities for operating leases with terms greater than one year. Operating lease right-of-use assets and liabilities are recorded at the present value of the fixed lease payments over the life of the lease. The majority of the Company's leases do not provide an implicit rate. Therefore, the Company uses its incremental borrowing rate at lease commencement to measure operating lease right-of-use assets and lease liabilities. Certain of the Company's leases provide for renewal and purchase options. Renewal and purchase options are evaluated at lease commencement and included in the lease term if they are reasonably certain to be exercised. Short-term leases are recognized in rental expense on a straight-line basis over the lease term and are not recorded in the consolidated balance sheets. The Company's finance leases are not material to the consolidated financial statements. Lease related asset and liability balances were as follows: June 30, Operating Leases Right-of-use assets $ 381 Accrued and other liabilities $ 91 Operating lease liabilities 294 Total operating lease liabilities $ 385 Weighted Average Remaining Term (in years) 7 Weighted Average Lease Discount Rate 3.5 % The Company's operating lease cost is comprised of payments related to operating leases recorded in the consolidated balance sheet and short-term rental payments for leases that are not recorded in the consolidated balance sheet. Variable operating lease cost was not material to the consolidated statement of operations for the three and six months ended June 30, 2019 . The components of operating lease expense were as follows: Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Operating lease cost (1) $ 28 $ 56 Short-term lease cost 14 28 Total operating lease cost $ 42 $ 84 _____________ (1) Includes fixed lease payments for operating leases recorded in the consolidated balance sheet. Maturities of lease liabilities were as follows at June 30, 2019 : Operating Leases 2019 (excluding the six months ended June 30, 2019) $ 54 2020 92 2021 71 2022 56 2023 43 Thereafter 147 Total lease payments 463 Less: imputed interest (78 ) Present value of lease liabilities $ 385 Future lease commitments for operating lease obligations were as follows at December 31, 2018 : Operating Leases 2019 $ 94 2020 89 2021 70 2022 56 2023 42 Thereafter 152 Total lease payments $ 503

Goodwill (Notes)

Goodwill (Notes)	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Goodwill The gross carrying amounts and changes in the carrying amount of goodwill for the six months ended June 30, 2019 were as follows: Olefins Segment Vinyls Segment Total Balances at December 31, 2018 $ 30 $ 972 $ 1,002 Goodwill acquired during the period — 74 74 Effects of changes in foreign exchange rates — 3 3 Balances at June 30, 2019 $ 30 $ 1,049 $ 1,079 The Company performed its annual impairment assessment for the Vinyls reporting units during the second quarter of 2019 and did not identify any impairment.

Accounts and Notes Payable (Not

Accounts and Notes Payable (Notes)	6 Months Ended
	Jun. 30, 2019
Accounts and Notes Payable [Abstract]
Accounts and Notes Payable	Accounts and Notes Payable Accounts and notes payable consist of the following: June 30, December 31, Accounts payable—third parties $ 494 $ 504 Accounts payable to related parties 1 2 Notes payable 26 1 Accounts and notes payable $ 521 $ 507

Long-Term Debt (Notes)

Long-Term Debt (Notes)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consists of the following: June 30, 2019 December 31, 2018 Principal Unamortized Discount Net Principal Unamortized Net 3.60% senior notes due 2022 (the "3.60% 2022 Senior Notes") $ 250 $ (1 ) $ 249 $ 250 $ (1 ) $ 249 3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes") 750 (8 ) 742 750 (9 ) 741 Loan related to tax-exempt waste disposal revenue bonds due 2027 11 — 11 11 — 11 6 ½% senior notes due 2029 (the "6 ½% 2029 GO Zone Senior Notes") 100 (1 ) 99 100 (1 ) 99 6 ½% senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes") 89 (1 ) 88 89 (1 ) 88 6 ½% senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes") 65 — 65 65 — 65 5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes") 700 (24 ) 676 700 (24 ) 676 4.375% senior notes due 2047 (the "4.375% 2047 Senior Notes") 500 (9 ) 491 500 (9 ) 491 3.50% senior notes due 2032 (the "3.50% 2032 GO Zone Refunding Senior Notes") 250 (2 ) 248 250 (2 ) 248 Total Long-term debt $ 2,715 $ (46 ) $ 2,669 $ 2,715 $ (47 ) $ 2,668 Credit Agreement The Company has a $1,000 revolving credit facility that is scheduled to mature on July 24, 2023 (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% in each case depending on the credit rating of the Company. At June 30, 2019 , the Company had no borrowings outstanding under the Credit Agreement. As of June 30, 2019 , the Company had no outstanding letters of credit and borrowing availability of $1,000 under the Credit Agreement. The Credit Agreement contains certain affirmative and negative covenants, including a quarterly total leverage ratio financial maintenance covenant. As of June 30, 2019 , the Company was in compliance with the total leverage ratio financial maintenance covenant. The Credit Agreement also contains certain events of default and if and for so long as certain events of default have occurred and are continuing, any overdue amounts outstanding under the Credit Agreement will accrue interest at an increased rate, the lenders can terminate their commitments thereunder and payments of any outstanding amounts could be accelerated by the lenders. None of the Company's subsidiaries are required to guarantee the obligations of the Company under the Credit Agreement. The Credit Agreement includes a $150 sub-limit for letters of credit, and any outstanding letters of credit will be deducted from availability under the facility. The Credit Agreement also provides for a discretionary $50 commitment for swingline loans to be provided on a same-day basis. The Company may also increase the size of the facility, in increments of at least $25 , up to a maximum of $500 , subject to certain conditions and if certain lenders agree to commit to such an increase. As of June 30, 2019 , the Company was in compliance with all of its long-term debt covenants. Unamortized debt issuance costs on long-term debt were $24 and $25 at June 30, 2019 and December 31, 2018 , respectively. On July 17, 2019, the Company closed the public offering of €700 million aggregate principal amount of 1.625% Senior Notes due July 17, 2029 (the "1.625% 2029 Senior Notes"). See Note 18 —

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss) (Notes)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Changes in accumulated other comprehensive income (loss) by component for the six months ended June 30, 2019 and 2018 were as follows: Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Total Balances at December 31, 2017 $ 43 $ (36 ) $ 7 Other comprehensive income (loss) before reclassifications — (40 ) (40 ) Net other comprehensive income (loss) attributable to Westlake Chemical Corporation — (40 ) (40 ) Balances at June 30, 2018 $ 43 $ (76 ) $ (33 ) Balances at December 31, 2018 $ 27 $ (89 ) $ (62 ) Other comprehensive income (loss) before reclassifications — 12 12 Net other comprehensive income (loss) attributable to Westlake Chemical Corporation — 12 12 Balances at June 30, 2019 $ 27 $ (77 ) $ (50 )

Fair Value Measurements (Notes)

Fair Value Measurements (Notes)	6 Months Ended
	Jun. 30, 2019
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 Company has financial assets and liabilities subject to fair value measures. These financial assets and liabilities include cash and cash equivalents, accounts receivable, net, accounts payable and long-term debt, all of which are recorded at carrying value. The amounts reported in the consolidated balance sheets for cash and cash equivalents, accounts receivable, net and accounts payable approximate their fair value due to the short maturities of these instruments. The carrying and fair values of the Company's long-term debt are summarized in the table below. The Company's long-term debt instruments are publicly-traded. A market approach, based upon quotes from financial reporting services, is used to measure the fair value of the Company's long-term debt. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy. June 30, 2019 December 31, 2018 Carrying Value Fair Value Carrying Value Fair Value 3.60% 2022 Senior Notes $ 249 $ 255 $ 249 $ 248 3.60% 2026 Senior Notes 742 761 741 692 Loan related to tax-exempt waste disposal revenue bonds due 2027 11 11 11 11 6 ½% 2029 GO Zone Senior Notes 99 104 99 106 6 ½% 2035 GO Zone Senior Notes 88 94 88 95 6 ½% 2035 IKE Zone Senior Notes 65 69 65 69 5.0% 2046 Senior Notes 676 721 676 641 4.375% 2047 Senior Notes 491 475 491 417 3.50% 2032 GO Zone Refunding Senior Notes 248 259 248 233

Income Taxes (Notes)

Income Taxes (Notes)	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective income tax rates were 23.2% and 24.4% for the three months ended June 30, 2019 and 2018 , respectively. The effective income tax rate for the three months ended June 30, 2019 was above the statutory rate of 21.0% primarily due to state taxes. The effective income tax rate for the three months ended June 30, 2018 was above the U.S. federal statutory rate of 21.0% primarily due to certain discrete adjustments related to foreign and state corporate rate changes and state and foreign taxes. The effective income tax rates were 24.9% and 23.7% for the six months ended June 30, 2019 and 2018 , respectively. The effective income tax rate for the six months ended June 30, 2019 was above the statutory rate of 21.0% primarily due to state taxes and the tax effect related to charges associated with the write-off of certain assets. The effective income tax rate for the six months ended June 30, 2018 was above the U.S. federal statutory rate of 21.0% primarily due to certain discrete adjustments related to foreign and state corporate rate changes and state and foreign taxes.

Earnings and Dividends per Shar

Earnings and Dividends per Share (Notes)	6 Months Ended
	Jun. 30, 2019
Earnings and Dividends Per Share [Abstract]
Earnings per Share	Earnings and Dividends per Share Earnings per Share The Company has unvested restricted stock units outstanding that are considered participating securities and, therefore, computes basic and diluted earnings per share under the two-class method. The computation of basic earnings per share is based upon the weighted average number of shares of common stock outstanding during each period. Diluted earnings per share includes the effects of certain stock options and performance stock units. Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net income attributable to Westlake Chemical Corporation $ 119 $ 278 $ 191 $ 565 Less: Net income attributable to participating securities (1 ) (2 ) (1 ) (3 ) Net income attributable to common shareholders $ 118 $ 276 $ 190 $ 562 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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Weighted average common shares—basic 128,485,182 129,624,291 128,506,712 129,554,528 Plus incremental shares from: Assumed exercise of options and vesting of performance stock units 365,153 682,324 375,240 694,556 Weighted average common shares—diluted 128,850,335 130,306,615 128,881,952 130,249,084 Earnings per common share attributable to Westlake Chemical Corporation: Basic $ 0.92 $ 2.13 $ 1.48 $ 4.34 Diluted $ 0.92 $ 2.12 $ 1.47 $ 4.31 Excluded from the computation of diluted earnings per share are options to purchase 562,342 and 172,642 shares of common stock for the three months ended June 30, 2019 and 2018 , respectively, and 442,076 and 128,892 shares of common stock for the six months ended June 30, 2019 and 2018 , respectively. These options were outstanding during the periods reported but were excluded because the effect of including them would have been antidilutive. Dividends per Share Dividends per common share for the three and six months ended June 30, 2019 and 2018 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Dividends per common share $ 0.25 $ 0.21 $ 0.50 $ 0.42

Supplemental Information (Notes

Supplemental Information (Notes)	6 Months Ended
	Jun. 30, 2019
Supplemental Information [Abstract]
Supplemental Information	Supplemental Information Other Assets, net The Company's investment in a joint venture with Lotte Chemical USA Corporation to build an ethylene facility, LACC, LLC, was $225 and $183 at June 30, 2019 and December 31, 2018 , respectively. Accrued and Other Liabilities Accrued and other liabilities were $733 and $676 at June 30, 2019 and December 31, 2018 , respectively. Accrued rebates, which are a component of accrued and other liabilities, were $93 and $125 at June 30, 2019 and December 31, 2018 , respectively. Other than the lease liability disclosed in Note 5, no other component of accrued and other liabilities was more than five percent of total current liabilities. Accrued liabilities with related parties were $38 and $54 at June 30, 2019 and December 31, 2018 , respectively. Restructuring, Transaction and Integration-related Costs For the three months ended June 30, 2019 , the restructuring, transaction and integration-related costs of $2 primarily consisted of integration-related consulting fees and costs associated with acquisitions. For the six months ended June 30, 2019 , the restructuring, transaction and integration-related costs primarily consisted of restructuring expenses of $19 related to certain Vinyls segment operations and integration-related consulting fees and costs associated with acquisitions of $5 . The restructuring expenses consisted of charges associated with the write-off of certain assets. Other Income, Net For the three months ended June 30, 2019 and 2018, other income, net of $2 and $8 , respectively, primarily consisted of income from unconsolidated subsidiaries and interest income on cash and cash equivalents. For the six months ended June 30, 2019 , other income, net included income from unconsolidated subsidiaries and interest income on cash and cash equivalents of $5 and $5 , respectively. For the six months ended June 30, 2018 , other income, net included income from unconsolidated subsidiaries, gain on redemption of senior notes and interest income on cash and cash equivalents of $12 , $6 and $6 , respectively. Non-cash Investing Activity The change in capital expenditure accrual resulted in an increase in additions to property, plant and equipment by $9 for t he six months ended June 30, 2019 . The change in capital expenditure accrual resulted in a decrease in additions to property, plant and equipment by $18 for the six months ended June 30, 2018 . Operating Lease Supplemental Cash Flow Supplemental cash flow information related to leases was as follows: Six Months Ended June 30, 2019 Operating cash flows from operating leases (1) $ 26 Right-of-use assets obtained in exchange for operating lease obligations 2 _____________ (1) Includes cash paid for amounts included in the measurement of operating lease liabilities recorded in the consolidated balance sheets. For the six months ended June 30, 2019 , finance lease related cash flows used for operating and financing activities were not material to the consolidated statement of cash flows.

Acquisition (Notes)

Acquisition (Notes)	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Acquisition	Acquisition NAKAN TM On January 2, 2019, the Company acquired all of the outstanding equity interests in the parent entity of the NAKAN TM global compounding solutions business. NAKAN's products are used in a wide-variety of applications, including in the automotive, building and construction, and medical industries. The closing purchase price of $249 was paid with available cash on hand. The acquisition is being accounted for under the acquisition method of accounting. The assets acquired and liabilities assumed and the results of operations of NAKAN are included in the Vinyls segment. NAKAN's net sales and earnings since the acquisition date were not material to the Company's consolidated statement of operations for the six months ended June 30, 2019 . The acquisition-related costs recognized in the consolidated statement of operation for the six months ended June 30, 2019 were not material. The pro forma impact of this business combination has not been presented as it is not material to the Company's consolidated statements of operations for the six months ended June 30, 2019 and 2018. The following table summarizes the estimated fair value of identified assets acquired and liabilities assumed at the date of acquisition. The preliminary allocation of consideration transferred is based on management's estimates, judgments and assumptions. When determining the fair values of assets acquired and liabilities assumed, management made significant estimates, judgments and assumptions. These estimates, judgments and assumptions are subject to change upon final valuation and should be treated as preliminary values. Management estimated that consideration paid exceeded the fair value of the net assets acquired. Therefore, goodwill of $40 was recorded. The goodwill recognized is primarily attributable to the expected values to be achieved from the acquisition. The information below represents the preliminary purchase price allocation: Cash $ 10 Accounts receivable 53 Inventories 40 Prepaid expenses and other current assets 7 Property, plant and equipment 75 Operating lease right-of-use assets 3 Intangible assets: Customer relationships (weighted average lives of 17 years) 65 Technology (weighted average lives of 14 years) 40 Trade name (life of 15 years) 25 Other assets 12 Total assets acquired 330 Accounts and notes payable 57 Accrued and other liabilities 18 Deferred income taxes 31 Pension and other post-retirement benefits 4 Operating lease liabilities 3 Other long-term liabilities 8 Total liabilities assumed 121 Total identifiable net assets acquired 209 Goodwill 40 Total purchase consideration $ 249

Commitments and Contingencies (

Commitments and Contingencies (Notes)	6 Months Ended
	Jun. 30, 2019
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 outcome 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, under certain circumstances, if required to recognize costs in a specific period, when combined with other factors, outcomes with respect to such matters may be material to the Company's consolidated statements of operations in such period. 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. The Company and other caustic soda producers were named as defendants in eight purported class action civil lawsuits filed in March, April and July 2019 in the U.S. District Court for the Western District of New York. The lawsuits allege the defendants conspired to fix, raise, maintain and stabilize the price of caustic soda, restrict domestic (U.S.) supply of caustic soda and allocate caustic soda customers. The other defendants named in the lawsuits are Olin Corporation, K.A. Steel Chemicals (a wholly owned subsidiary of Olin), Occidental Petroleum Corporation, Occidental Chemical Corporation d/b/a OxyChem, Shin-Etsu Chemical Co., Ltd., Shintech Incorporated, Formosa Plastics Corporation, and Formosa Plastics Corporation, U.S.A. The lawsuits are filed on behalf of the respective named plaintiffs and a putative class comprised of all persons and entities who purchased caustic soda in the U.S. directly from one or more of the defendants, their parents, predecessors, subsidiaries or affiliates at any time between October 1, 2015 and the present. Plaintiffs seek an unspecified amount of damages and injunctive relief. The Company believes the claims are without merit and intends to defend against them vigorously. At this time, the Company is not able to estimate the impact, if any, that these lawsuits could have on the Company's consolidated financial statements either in the current period or in future periods. Environmental. As of June 30, 2019 and December 31, 2018 , the Company had reserves for environmental contingencies totaling approximately $49 and $54 , 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. Calvert City Proceedings. For several years, the Environmental Protection Agency (the "EPA") has been conducting remedial investigation and feasibility studies at the Company's Calvert City, Kentucky facility pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 ("CERCLA"). As the current owner of the Calvert City facility, the Company was named by the EPA as a potentially responsible party ("PRP") along with Goodrich Corporation ("Goodrich") and its successor-in-interest, PolyOne Corporation ("PolyOne"). On November 30, 2017, the EPA published a draft Proposed Plan, incorporating by reference an August 2015 draft Remedial Investigation ("RI") report, an October 2017 draft Feasibility Study ("FS") report and a new Technical Impracticability Waiver document dated December 19, 2017. On June 18, 2018, the EPA published an amendment to its Proposed Plan. The amended Proposed Plan describes a final remedy for the onshore portion of the site comprised of a containment wall, targeted treatment and supplemental hydraulic containment. The amended Proposed Plan also describes an interim approach to address the contamination under the river that would include recovery of any mobile contaminants by an extraction well along with further study of the extent of the contamination and potential treatment options. The EPA's estimated cost of implementation is $107 , with an estimated $1 to $3 in annual operation and maintenance ("O&M") costs. In September 2018, the EPA published the Record of Decision ("ROD") for the site, formally selecting the preferred final and interim remedies outlined in the amended Proposed Plan. In October 2018, EPA issued Special Notice letters to the PRPs for the remedial design phase of work under the ROD. In April 2019, the PRPs and the EPA entered into an Administrative Settlement Agreement and Order on Consent for Remedial Design. The Company's allocation of liability for remedial and O&M costs at the Calvert City site, if any, is governed by a series of agreements between the Company, Goodrich and PolyOne. These agreements are the subject of further litigation as described below. In connection with the 1990 and 1997 acquisitions of the Goodrich chemical manufacturing complex in Calvert City, Goodrich agreed to indemnify the Company for any liabilities related to preexisting contamination at the complex. For its part, the Company agreed to indemnify Goodrich for post-closing contamination caused by the Company's operations. The soil and groundwater at the complex, which does not include the Company's nearby PVC facility, had been extensively contaminated by Goodrich's operations. In 1993, Goodrich spun off the predecessor of PolyOne, and that predecessor assumed Goodrich's indemnification obligations relating to preexisting contamination. In 2003, litigation arose among the Company, Goodrich and PolyOne with respect to the allocation of the cost of remediating contamination at the site. The parties settled this litigation in December 2007 and the case was dismissed. In the settlement, the parties agreed that, among other things: (1) PolyOne would pay 100% of the costs (with specified exceptions), net of recoveries or credits from third parties, incurred with respect to environmental issues at the Calvert City site from August 1, 2007 forward; and (2) either the Company or PolyOne might, from time to time in the future (but not more than once every five years), institute an arbitration proceeding to adjust that percentage. In May 2017, PolyOne filed a demand for arbitration. In this proceeding, PolyOne sought to readjust the percentage allocation of future costs and to recover approximately $11 from the Company in reimbursement of previously paid remediation costs. The Company's cross demand for arbitration seeking unreimbursed remediation costs incurred during the relevant period was dismissed from the proceedings when PolyOne made payment in full at the beginning of the arbitration hearing. On July 10, 2018, PolyOne sued the Company in the U.S. District Court for the Western District of Kentucky, and sought to invalidate the arbitration provisions in the parties' 2007 settlement agreement and enjoin the arbitration it had initiated in 2017. On July 30, 2018, the district court refused to enjoin the arbitration and, on January 15, 2019, the court granted the Company's motion to dismiss PolyOne's suit. On February 13, 2019, PolyOne appealed those decisions to the U.S. Court of Appeals for the Sixth Circuit. Oral argument in that appeal is scheduled for August 1, 2019. The arbitration hearing began in August 2018 and concluded in December 2018. On May 22, 2019, the arbitration panel issued its final award. It determined that PolyOne was responsible for 100% of the allocable costs at issue in the proceeding and that PolyOne would remain responsible for 100% of the costs to operate the existing groundwater remedy at the Calvert City site. This determination is subject to further litigation. At this time, the Company is not able to estimate the impact, if any, that the issuance of the final award in the arbitration proceeding, or any subsequent judicial proceeding, could have on the Company's consolidated financial statements either in the current period or in later periods. Any cash expenditures that the Company might incur in the future with respect to the remediation of contamination at the Calvert City complex would likely be spread out over an extended period. As a result, the Company believes it is unlikely that any remediation costs allocable to it will be material in terms of expenditures made in any individual reporting period. Environmental Remediation: Reasonably Possible Matters. The Company's assessment of the potential impact of environmental contingencies is subject to considerable uncertainty due to the complex, ongoing and evolving process of investigation and remediation, if necessary, of such environmental contingencies, and the potential for technological and regulatory developments. As such, in addition to the amounts currently reserved, the Company may be subject to reasonably possible loss contingencies related to environmental matters in the range of $65 to $130 .

Segment Information (Notes)

Segment Information (Notes)	6 Months Ended
	Jun. 30, 2019
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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net external sales Olefins Polyethylene $ 345 $ 387 $ 682 $ 756 Styrene, feedstock and other 132 95 254 229 Total Olefins 477 482 936 985 Vinyls PVC, caustic soda and other 1,319 1,396 2,626 2,754 Building products 348 357 607 646 Total Vinyls 1,667 1,753 3,233 3,400 $ 2,144 $ 2,235 $ 4,169 $ 4,385 Intersegment sales Olefins $ 74 $ 112 $ 166 $ 232 Vinyls 1 1 1 1 $ 75 $ 113 $ 167 $ 233 Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Income (loss) from operations Olefins $ 82 $ 158 $ 119 $ 321 Vinyls 129 271 230 537 Corporate and other (17 ) (25 ) (21 ) (53 ) $ 194 $ 404 $ 328 $ 805 Depreciation and amortization Olefins $ 36 $ 33 $ 71 $ 67 Vinyls 138 120 272 238 Corporate and other 2 3 4 7 $ 176 $ 156 $ 347 $ 312 Other income (loss), net Olefins $ 1 $ 1 $ 3 $ 3 Vinyls 2 4 6 16 Corporate and other (1 ) 3 2 11 $ 2 $ 8 $ 11 $ 30 Provision for (benefit from) income taxes Olefins $ 18 $ 36 $ 27 $ 73 Vinyls 22 69 45 130 Corporate and other (1 ) (12 ) (2 ) (21 ) $ 39 $ 93 $ 70 $ 182 Capital expenditures Olefins $ 37 $ 26 $ 62 $ 48 Vinyls 169 128 346 258 Corporate and other 2 4 3 6 $ 208 $ 158 $ 411 $ 312 A reconciliation of total segment income from operations to consolidated income before income taxes is as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Income from operations $ 194 $ 404 $ 328 $ 805 Interest expense (28 ) (31 ) (58 ) (68 ) Other income, net 2 8 11 30 Income before income taxes $ 168 $ 381 $ 281 $ 767 June 30, December 31, Total assets Olefins $ 2,057 $ 2,024 Vinyls 9,766 8,879 Corporate and other 393 699 $ 12,216 $ 11,602

Westlake Chemical Partners LP (

Westlake Chemical Partners LP (Notes)	6 Months Ended
	Jun. 30, 2019
Partners' Capital [Abstract]
Westlake Chemical Partners LP	Westlake Chemical Partners LP In 2014, the Company formed Westlake Chemical Partners LP ("WLKP") to operate, acquire and develop ethylene production facilities and related assets. Also in 2014, WLKP completed its initial public offering of 12,937,500 common units. On March 29, 2019, WLKP purchased an additional 4.5% newly issued limited partner interest in Westlake Chemical OpCo LP ("OpCo") for approximately $201 and completed a private placement of 2,940,818 common units at a price of $21.40 per common unit for total proceeds of approximately $63 . TTWF LP, the Company's principal stockholder and a related party, acquired 1,401,869 units out of 2,940,818 common units issued in the private placement. At June 30, 2019 , WLKP had a 22.8% limited partner interest in OpCo, and the Company retained a 77.2% limited partner interest in OpCo and a significant interest in WLKP through the Company's ownership of WLKP's general partner, 40.1% of limited partner interest (consisting of 14,122,230 common units) and incentive distribution rights.

Subsequent Event (Notes)

Subsequent Event (Notes)	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Event On July 17, 2019, the Company closed the public offering of €700 million aggregate principal amount of 1.625% 2029 Senior Notes. The Company received approximately $779 of net proceeds from the offering. The 1.625% 2029 Senior Notes will accrue interest from July 17, 2019 at a rate of 1.625% per annum, payable annually in arrears on July 17 of each year, beginning July 17, 2020. The terms of the 1.625%

Basis of Financial Statements_2

Basis of Financial Statements (Policies)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Financial Statements	The accompanying unaudited consolidated interim financial statements were prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the "SEC") for interim periods. Accordingly, certain information and footnotes required for complete financial statements under generally accepted accounting principles in the United States ("U.S. GAAP") have not been included. These interim consolidated financial statements should be read in conjunction with the 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, 2018 (the " 2018 Form 10-K"), filed with the SEC on February 20, 2019 . 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, 2018 with the exception of those accounting standards adopted in 2019 as discussed in Note 1. In the opinion of the Company's management, the accompanying unaudited consolidated interim financial statements reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company's financial position as of June 30, 2019 , its results of operations for the three and six months ended June 30, 2019 and 2018 , and the changes in its cash position for the six months ended June 30, 2019 and 2018 . 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, 2019 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 Credit Losses (ASU No. 2016-13) In June 2016, the Financial Accounting Standards Board ("FASB") issued an accounting standards update providing new guidance for the accounting for credit losses on loans and other financial instruments. The new guidance introduces an approach based on expected losses to estimate credit losses on certain types of financial instruments. The standard also modifies the impairment model for available-for-sale debt securities and provides for a simplified accounting model for purchased financial assets with credit deterioration since their origination. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Intangibles - Goodwill and Other (ASU No. 2017-04) In January 2017, the FASB issued an accounting standards update to simplify the subsequent measurement of goodwill. The guidance removes Step 2 of the goodwill impairment test, which requires a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. The accounting standard will be effective for reporting periods beginning after December 15, 2019 and is not expected to have a material impact on the Company's consolidated financial position, results of operations and cash flows. Fair Value Measurement (ASU No. 2018-13) In August 2018, the FASB issued an accounting standards update to modify the disclosure requirements on fair value measurements. The amendments are effective for periods beginning after December 15, 2019. An entity is permitted to early adopt any removed or modified disclosures and delay adoption of the additional disclosures until the effective date. Most amendments should be applied retrospectively, but certain amendments will be applied prospectively. The Company is in the process of assessing the impact of the standard on the Company's fair value disclosures. However, the standard is not expected to have an impact on the Company's consolidated financial position, results of operations and cash flows. Recently Adopted Accounting Standards Leases (ASU No. 2016-02) In February 2016, the FASB issued an accounting standards update on lease accounting that supersedes the previously issued leases guidance. The new standard requires lessees to recognize assets and liabilities for all long-term operating leases. An asset is recognized for the right to use an underlying leased asset and a liability is recognized for the obligation to make payments over the lease term. The standard also requires expanded lease disclosures. The standard requires a modified retrospective adoption approach and allows for the election of certain transition expedients. The Company adopted the standard January 1, 2019 using the optional transition method which allows entities to recognize a cumulative adjustment to the opening balance sheet in the period of adoption. The Company elected the package of optional transition expedients and was not required to reassess (1) whether any existing contracts are or contain leases, (2) classification of existing leases as operating or capital or (3) whether initial direct costs for existing leases qualify for capitalization under the new accounting standard. The Company did not elect the use of hindsight to determine the lease term when considering lease renewal or termination options. Additionally, the Company elected to continue accounting for existing land easements under its accounting policies that were in effect prior to adoption of the new lease standard. The following amounts were recorded as a result of adopting the new lease standard on January 1, 2019: Operating Lease Assets and Liabilities Balance Sheet Location Amounts Recorded in the Consolidated Balance Sheet January 1, 2019 Right-of-use assets Operating lease right-of-use assets $ 421 Current lease liabilities Accrued and other liabilities (94 ) Non-current lease liabilities Operating lease liabilities (331 ) Deferred rent Other liabilities 4

Accounts Receivable (Tables)

Accounts Receivable (Tables)	6 Months Ended
	Jun. 30, 2019
Accounts Receivable, Net [Abstract]
Schedule Of Accounts Receivable	Accounts receivable consist of the following: June 30, December 31, Trade customers $ 1,152 $ 969 Related parties 8 6 Allowance for doubtful accounts (24 ) (23 ) 1,136 952 Federal and state taxes 51 57 Other 26 28 Accounts receivable, net $ 1,213 $ 1,037

Inventories (Tables)

Inventories (Tables)	6 Months Ended
	Jun. 30, 2019
Inventory Disclosure [Abstract]
Schedule Of Inventory	Inventories consist of the following: June 30, December 31, Finished products $ 558 $ 657 Feedstock, additives, chemicals and other raw materials 212 203 Materials and supplies 155 154 Inventories $ 925 $ 1,014

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lease related asset and liability	Lease related asset and liability balances were as follows: June 30, Operating Leases Right-of-use assets $ 381 Accrued and other liabilities $ 91 Operating lease liabilities 294 Total operating lease liabilities $ 385 Weighted Average Remaining Term (in years) 7 Weighted Average Lease Discount Rate 3.5 %
Lease, Cost	The components of operating lease expense were as follows: Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Operating lease cost (1) $ 28 $ 56 Short-term lease cost 14 28 Total operating lease cost $ 42 $ 84 _____________ (1) Includes fixed lease payments for operating leases recorded in the consolidated balance sheet.
Maturities of Operating Lease Liabilities	Maturities of lease liabilities were as follows at June 30, 2019 : Operating Leases 2019 (excluding the six months ended June 30, 2019) $ 54 2020 92 2021 71 2022 56 2023 43 Thereafter 147 Total lease payments 463 Less: imputed interest (78 ) Present value of lease liabilities $ 385
Schedule of Future Lease Commitments for Operating Leases	Future lease commitments for operating lease obligations were as follows at December 31, 2018 : Operating Leases 2019 $ 94 2020 89 2021 70 2022 56 2023 42 Thereafter 152 Total lease payments $ 503

Goodwill (Tables)

Goodwill (Tables)	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The gross carrying amounts and changes in the carrying amount of goodwill for the six months ended June 30, 2019 were as follows: Olefins Segment Vinyls Segment Total Balances at December 31, 2018 $ 30 $ 972 $ 1,002 Goodwill acquired during the period — 74 74 Effects of changes in foreign exchange rates — 3 3 Balances at June 30, 2019 $ 30 $ 1,049 $ 1,079

Accounts and Notes Payable (Tab

Accounts and Notes Payable (Tables)	6 Months Ended
	Jun. 30, 2019
Accounts and Notes Payable [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	Accounts and notes payable consist of the following: June 30, December 31, Accounts payable—third parties $ 494 $ 504 Accounts payable to related parties 1 2 Notes payable 26 1 Accounts and notes payable $ 521 $ 507

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Schedule Of Long-Term Debt	Long-term debt consists of the following: June 30, 2019 December 31, 2018 Principal Unamortized Discount Net Principal Unamortized Net 3.60% senior notes due 2022 (the "3.60% 2022 Senior Notes") $ 250 $ (1 ) $ 249 $ 250 $ (1 ) $ 249 3.60% senior notes due 2026 (the "3.60% 2026 Senior Notes") 750 (8 ) 742 750 (9 ) 741 Loan related to tax-exempt waste disposal revenue bonds due 2027 11 — 11 11 — 11 6 ½% senior notes due 2029 (the "6 ½% 2029 GO Zone Senior Notes") 100 (1 ) 99 100 (1 ) 99 6 ½% senior notes due 2035 (the "6 ½% 2035 GO Zone Senior Notes") 89 (1 ) 88 89 (1 ) 88 6 ½% senior notes due 2035 (the "6 ½% 2035 IKE Zone Senior Notes") 65 — 65 65 — 65 5.0% senior notes due 2046 (the "5.0% 2046 Senior Notes") 700 (24 ) 676 700 (24 ) 676 4.375% senior notes due 2047 (the "4.375% 2047 Senior Notes") 500 (9 ) 491 500 (9 ) 491 3.50% senior notes due 2032 (the "3.50% 2032 GO Zone Refunding Senior Notes") 250 (2 ) 248 250 (2 ) 248 Total Long-term debt $ 2,715 $ (46 ) $ 2,669 $ 2,715 $ (47 ) $ 2,668

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Changes in accumulated other comprehensive income (loss) by component for the six months ended June 30, 2019 and 2018 were as follows: Benefits Liability, Net of Tax Cumulative Foreign Currency Exchange, Net of Tax Total Balances at December 31, 2017 $ 43 $ (36 ) $ 7 Other comprehensive income (loss) before reclassifications — (40 ) (40 ) Net other comprehensive income (loss) attributable to Westlake Chemical Corporation — (40 ) (40 ) Balances at June 30, 2018 $ 43 $ (76 ) $ (33 ) Balances at December 31, 2018 $ 27 $ (89 ) $ (62 ) Other comprehensive income (loss) before reclassifications — 12 12 Net other comprehensive income (loss) attributable to Westlake Chemical Corporation — 12 12 Balances at June 30, 2019 $ 27 $ (77 ) $ (50 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary Of Carrying And Fair Values Of Long-Term Debt	The carrying and fair values of the Company's long-term debt are summarized in the table below. The Company's long-term debt instruments are publicly-traded. A market approach, based upon quotes from financial reporting services, is used to measure the fair value of the Company's long-term debt. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy. June 30, 2019 December 31, 2018 Carrying Value Fair Value Carrying Value Fair Value 3.60% 2022 Senior Notes $ 249 $ 255 $ 249 $ 248 3.60% 2026 Senior Notes 742 761 741 692 Loan related to tax-exempt waste disposal revenue bonds due 2027 11 11 11 11 6 ½% 2029 GO Zone Senior Notes 99 104 99 106 6 ½% 2035 GO Zone Senior Notes 88 94 88 95 6 ½% 2035 IKE Zone Senior Notes 65 69 65 69 5.0% 2046 Senior Notes 676 721 676 641 4.375% 2047 Senior Notes 491 475 491 417 3.50% 2032 GO Zone Refunding Senior Notes 248 259 248 233

Earnings and Dividends per Sh_2

Earnings and Dividends per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings and Dividends Per Share [Abstract]
Schedule Of Net Income Attributable To Common Stockholders	Diluted earnings per share includes the effects of certain stock options and performance stock units. Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net income attributable to Westlake Chemical Corporation $ 119 $ 278 $ 191 $ 565 Less: Net income attributable to participating securities (1 ) (2 ) (1 ) (3 ) Net income attributable to common shareholders $ 118 $ 276 $ 190 $ 562
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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Weighted average common shares—basic 128,485,182 129,624,291 128,506,712 129,554,528 Plus incremental shares from: Assumed exercise of options and vesting of performance stock units 365,153 682,324 375,240 694,556 Weighted average common shares—diluted 128,850,335 130,306,615 128,881,952 130,249,084 Earnings per common share attributable to Westlake Chemical Corporation: Basic $ 0.92 $ 2.13 $ 1.48 $ 4.34 Diluted $ 0.92 $ 2.12 $ 1.47 $ 4.31
Dividends Per Share	Dividends per Share Dividends per common share for the three and six months ended June 30, 2019 and 2018 were as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Dividends per common share $ 0.25 $ 0.21 $ 0.50 $ 0.42

Supplemental Information Operat

Supplemental Information Operating Lease Supplemental Cash Flow (Tables)	6 Months Ended
	Jun. 30, 2019
Supplemental Cash Flow Elements [Abstract]
Schedule of Operating Lease Supplemental Cash Flow	Operating Lease Supplemental Cash Flow Supplemental cash flow information related to leases was as follows: Six Months Ended June 30, 2019 Operating cash flows from operating leases (1) $ 26 Right-of-use assets obtained in exchange for operating lease obligations 2 _____________ (1) Includes cash paid for amounts included in the measurement of operating lease liabilities recorded in the consolidated balance sheets. For the six months ended June 30, 2019 , finance lease related cash flows used for operating and financing activities were not material to the consolidated statement of cash flows.

Acquisition (Tables)

Acquisition (Tables)	6 Months Ended
	Jun. 30, 2019
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The information below represents the preliminary purchase price allocation: Cash $ 10 Accounts receivable 53 Inventories 40 Prepaid expenses and other current assets 7 Property, plant and equipment 75 Operating lease right-of-use assets 3 Intangible assets: Customer relationships (weighted average lives of 17 years) 65 Technology (weighted average lives of 14 years) 40 Trade name (life of 15 years) 25 Other assets 12 Total assets acquired 330 Accounts and notes payable 57 Accrued and other liabilities 18 Deferred income taxes 31 Pension and other post-retirement benefits 4 Operating lease liabilities 3 Other long-term liabilities 8 Total liabilities assumed 121 Total identifiable net assets acquired 209 Goodwill 40 Total purchase consideration $ 249

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2019
Segment Reporting [Abstract]
Segment Reporting Information	Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net external sales Olefins Polyethylene $ 345 $ 387 $ 682 $ 756 Styrene, feedstock and other 132 95 254 229 Total Olefins 477 482 936 985 Vinyls PVC, caustic soda and other 1,319 1,396 2,626 2,754 Building products 348 357 607 646 Total Vinyls 1,667 1,753 3,233 3,400 $ 2,144 $ 2,235 $ 4,169 $ 4,385 Intersegment sales Olefins $ 74 $ 112 $ 166 $ 232 Vinyls 1 1 1 1 $ 75 $ 113 $ 167 $ 233 Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Income (loss) from operations Olefins $ 82 $ 158 $ 119 $ 321 Vinyls 129 271 230 537 Corporate and other (17 ) (25 ) (21 ) (53 ) $ 194 $ 404 $ 328 $ 805 Depreciation and amortization Olefins $ 36 $ 33 $ 71 $ 67 Vinyls 138 120 272 238 Corporate and other 2 3 4 7 $ 176 $ 156 $ 347 $ 312 Other income (loss), net Olefins $ 1 $ 1 $ 3 $ 3 Vinyls 2 4 6 16 Corporate and other (1 ) 3 2 11 $ 2 $ 8 $ 11 $ 30 Provision for (benefit from) income taxes Olefins $ 18 $ 36 $ 27 $ 73 Vinyls 22 69 45 130 Corporate and other (1 ) (12 ) (2 ) (21 ) $ 39 $ 93 $ 70 $ 182 Capital expenditures Olefins $ 37 $ 26 $ 62 $ 48 Vinyls 169 128 346 258 Corporate and other 2 4 3 6 $ 208 $ 158 $ 411 $ 312
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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Income from operations $ 194 $ 404 $ 328 $ 805 Interest expense (28 ) (31 ) (58 ) (68 ) Other income, net 2 8 11 30 Income before income taxes $ 168 $ 381 $ 281 $ 767
Total Assets	June 30, December 31, Total assets Olefins $ 2,057 $ 2,024 Vinyls 9,766 8,879 Corporate and other 393 699 $ 12,216 $ 11,602

Basis of Financial Statements C

Basis of Financial Statements Changes Due to Lease Standard Adoption (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 381		$ 0
Accrued and other liabilities	91
Operating lease liabilities	294		0
Other liabilities	$ 200		$ 179
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		$ 421
Operating lease liabilities		(331)
Accounting Standards Update 2016-02 [Member] | Accrued and Other Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued and other liabilities		(94)
Accounting Standards Update 2016-02 [Member] | Other Liabilities [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other liabilities		$ 4

Financial Instruments (Cash Equ

Financial Instruments (Cash Equivalent) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Debt Securities, Held-to-maturity	$ 50	$ 10

Financial Instruments (Restrict

Financial Instruments (Restricted Cash Equivalents) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Restricted Cash and Cash Equivalents	$ 22	$ 22

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts Receivable, Net [Abstract]
Trade customers	$ 1,152	$ 969
Related parties	8	6
Allowance for doubtful accounts	(24)	(23)
Accounts receivable from trade customers, net	1,136	952
Federal and state taxes	51	57
Other	26	28
Accounts receivable, net	$ 1,213	$ 1,037

Inventories (Details)

Inventories (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Finished products	$ 558	$ 657
Feedstock, additives, chemicals and other raw materials	212	203
Materials and supplies	155	154
Inventories	$ 925	$ 1,014

Leases (Details)

Leases (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Assets and Liabilities, Lessee [Abstract]
Operating lease right-of-use assets	$ 381	$ 381	$ 0
Accrued and other liabilities	91	91
Operating lease liabilities	294	294	0
Total Operating lease liabilities	$ 385	$ 385
Weighted Average Remaining Term (in years)	7 years	7 years
Weighted Average Lease Discount Rate	3.50%	3.50%
Lease, Cost [Abstract]
Operating lease cost	$ 28	$ 56
Short-term lease cost	14	28
Total operating lease cost	42	84
Operating Lease Liabilities, Payments Due [Abstract]
2019 (excluding the six months ended June 30, 2019)	54	54
2020	92	92
2021	71	71
2022	56	56
2023	43	43
Thereafter	147	147
Total lease payments	463	463
Less: imputed interest	$ (78)	$ (78)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019			94
2020			89
2021			70
2022			56
2023			42
Thereafter			152
Total lease payments			$ 503

Goodwill (Details)

Goodwill (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 1,002
Goodwill acquired during the period	74
Effects of changes in foreign exchange rates	3
Ending Balance	1,079
Olefins [Member]
Goodwill [Roll Forward]
Beginning Balance	30
Goodwill acquired during the period	0
Effects of changes in foreign exchange rates	0
Ending Balance	30
Vinyls [Member]
Goodwill [Roll Forward]
Beginning Balance	972
Goodwill acquired during the period	74
Effects of changes in foreign exchange rates	3
Ending Balance	$ 1,049

Accounts and Notes Payable (Det

Accounts and Notes Payable (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts and Notes Payable [Abstract]
Accounts payable—third parties	$ 494	$ 504
Accounts payable to related parties	1	2
Notes payable	26	1
Accounts and notes payable	$ 521	$ 507

Long-Term Debt (Schedule of Lon

Long-Term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal Amount	$ 2,715	$ 2,715
Unamortized Premium (Discount) and Debt Issuance Costs	(46)	(47)
Net, Long-term Debt	$ 2,669	2,668
Senior Notes [Member] | 3.60% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2022
Stated interest rate (percent)	3.60%
Principal Amount	$ 250	250
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 249	249
Senior Notes [Member] | 3.6% Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2026
Stated interest rate (percent)	3.60%
Principal Amount	$ 750	750
Unamortized Premium (Discount) and Debt Issuance Costs	(8)	(9)
Net, Long-term Debt	$ 742	741
Senior Notes [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2027
Principal Amount	$ 11	11
Unamortized Premium (Discount) and Debt Issuance Costs	0	0
Net, Long-term Debt	$ 11	11
Senior Notes [Member] | 6 1/2% GO Zone Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2029
Stated interest rate (percent)	6.50%
Principal Amount	$ 100	100
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 99	99
Senior Notes [Member] | 2035 GO Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 89	89
Unamortized Premium (Discount) and Debt Issuance Costs	(1)	(1)
Net, Long-term Debt	$ 88	88
Senior Notes [Member] | 2035 IKE Zone 6 1/2% Notes [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
Principal Amount	$ 65	65
Unamortized Premium (Discount) and Debt Issuance Costs	0	0
Net, Long-term Debt	$ 65	65
Senior Notes [Member] | 5.0% Senior Notes Due 2046 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2046
Stated interest rate (percent)	5.00%
Principal Amount	$ 700	700
Unamortized Premium (Discount) and Debt Issuance Costs	(24)	(24)
Net, Long-term Debt	$ 676	676
Senior Notes [Member] | 4.375% Senior Notes Due 2047 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2047
Stated interest rate (percent)	4.375%
Principal Amount	$ 500	500
Unamortized Premium (Discount) and Debt Issuance Costs	(9)	(9)
Net, Long-term Debt	$ 491	491
Senior Notes [Member] | 3.50% Senior Notes Due 2032 [Member]
Debt Instrument [Line Items]
Debt Instrument Maturity	2032
Stated interest rate (percent)	3.50%
Principal Amount	$ 250	250
Unamortized Premium (Discount) and Debt Issuance Costs	(2)	(2)
Net, Long-term Debt	$ 248	$ 248

Long-Term Debt (Credit Agreemen

Long-Term Debt (Credit Agreement) (Details) - Credit Agreement [Member] - USD ($) $ in Millions	Jul. 24, 2018	Jun. 30, 2019
Line of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of credit permitted increase	$ 25
Line of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of credit permitted increase	500
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity		$ 1,000
Revolving Credit Facility [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		1,000
Amount outstanding		0
Outstanding letters of credit		$ 0
Letter of Credit [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	150
Swingline Loan [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50
Alternate Base Rate [Domain] | Revolving Credit Facility [Member] | Line of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate	0.00%
Alternate Base Rate [Domain] | Revolving Credit Facility [Member] | Line of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate	0.75%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | Minimum [Member]
Debt Instrument [Line Items]
Spread on variable rate	1.00%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Line of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Spread on variable rate	1.75%

Long-Term Debt (Narrative) (Det

Long-Term Debt (Narrative) (Details) € in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)	Jul. 17, 2019EUR (€)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Document Period End Date	Jun. 30, 2019
Unamortized Debt Issuance Cost | $	$ 24		$ 25
Subsequent Event [Member] | Senior Notes [Member] | One Point Six Two Five Percentage Senior Notes Due Twenty Twenty Nine [Member] [Domain]
Debt Instrument [Line Items]
Stated interest rate (percent)		1.625%
Debt Instrument, Face Amount | €		€ 700

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 5,590
Ending balance	5,719
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	27	$ 43
Other comprehensive income (loss) before reclassifications	0	0
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	0	0
Ending balance	27	43
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(89)	(36)
Other comprehensive income (loss) before reclassifications	12	(40)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	12	(40)
Ending balance	(77)	(76)
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(62)	7
Other comprehensive income (loss) before reclassifications	12	(40)
Net other comprehensive income (loss) attributable to Westlake Chemical Corporation	12	(40)
Ending balance	$ (50)	$ (33)

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Carrying and Fair Values of Long Term Debt) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 2,669	$ 2,668
3.60% Senior Notes Due 2022 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 249	249
Debt Instrument Maturity	2022
Stated interest rate (percent)	3.60%
3.6% Senior Notes Due 2026 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 742	741
Debt Instrument Maturity	2026
Stated interest rate (percent)	3.60%
Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 11	11
Debt Instrument Maturity	2027
6 1/2% GO Zone Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 99	99
Debt Instrument Maturity	2029
Stated interest rate (percent)	6.50%
2035 GO Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 88	88
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
2035 IKE Zone 6 1/2% Notes [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 65	65
Debt Instrument Maturity	2035
Stated interest rate (percent)	6.50%
5.0% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 676	676
Debt Instrument Maturity	2046
Stated interest rate (percent)	5.00%
4.375% Senior Notes Due 2047 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 491	491
Debt Instrument Maturity	2047
Stated interest rate (percent)	4.375%
3.50% Senior Notes Due 2032 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 248	248
Debt Instrument Maturity	2032
Stated interest rate (percent)	3.50%
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	248
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	761	692
Fair Value [Member] | Loan related to tax-exempt waste disposal revenue bonds due 2027 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	11	11
Fair Value [Member] | 6 1/2% GO Zone Senior Notes Due 2029 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	104	106
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	94	95
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	69	69
Fair Value [Member] | 5.0% Senior Notes Due 2046 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	721	641
Fair Value [Member] | 4.375% Senior Notes Due 2047 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	475	417
Fair Value [Member] | 3.50% Senior Notes Due 2032 [Member] | Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 259	$ 233

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate	23.20%	24.40%	24.90%	23.70%
U.S. federal statutory income tax rate	21.00%	21.00%	21.00%	21.00%

Earnings and Dividends per Sh_3

Earnings and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings and Dividends Per Share [Abstract]
Net income attributable to Westlake Chemical Corporation	$ 119	$ 278	$ 191	$ 565
Net income attributable to participating securities	(1)	(2)	(1)	(3)
Net income attributable to common shareholders	$ 118	$ 276	$ 190	$ 562

Earnings and Dividends per Sh_4

Earnings and Dividends per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings and Dividends Per Share [Abstract]
Weighted average common shares—basic	128,485,182	129,624,291	128,506,712	129,554,528
Weighted Average Number Diluted Shares Outstanding Adjustment	365,153	682,324	375,240	694,556
Weighted average common shares-diluted	128,850,335	130,306,615	128,881,952	130,249,084
Earnings per share attributable to Westlake Chemical Corporation: Basic	$ 0.92	$ 2.13	$ 1.48	$ 4.34
Earnings per share attributable to Westlake Chemical Corporation: Diluted	$ 0.92	$ 2.12	$ 1.47	$ 4.31

Earnings and Dividends per Sh_5

Earnings and Dividends per Share (Additional Information) (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings and Dividends Per Share [Abstract]
Number of options excluded from computation of diluted earnings per share	562,342	172,642	442,076	128,892

Earnings and Dividends per Sh_6

Earnings and Dividends per Share Dividends Per Share (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings and Dividends Per Share [Abstract]
Dividends per common share (in usd per share)	$ 0.25	$ 0.21	$ 0.50	$ 0.42

Supplemental Information (Other

Supplemental Information (Other Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
LACC [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 225	$ 183

Supplemental Information (Addit

Supplemental Information (Additional Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Document Period End Date			Jun. 30, 2019
Accrued and other liabilities	$ 733		$ 733		$ 676
Accrued Rebates, Current	93		93		125
Due to Affiliate, Current	38		38		$ 54
Restructuring, transaction and integration-related costs	2	$ 8	24	$ 15
Restructuring Charges			19
Other income, net	$ 2	$ 8	11	30
Income (Loss) from Subsidiaries, Net of Tax			5	12
Gain on debt redemption				6
Interest Income, Other			5	6
Increase (Decrease) in Capital Expenditure Accrual			9	$ (18)
Vinyls [Member]
Business Combination, Acquisition Related Costs			$ 5

Supplemental Information (Opera

Supplemental Information (Operating Lease Supplemental Cash Flow) (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Supplemental Cash Flow Elements [Abstract]
Operating cash flows from operating leases	$ 26
Right-of-use assets obtained in exchange for operating lease obligations	$ 2

Acquisition (Details)

Acquisition (Details) - USD ($) $ in Millions	Jan. 02, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Revenues		$ 2,144	$ 2,235	$ 4,169	$ 4,385
Goodwill				74
Customer Relationships [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	17 years
Technology-Based Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	14 years
Trade Names [Member]
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Vinyls [Member]
Business Acquisition [Line Items]
Goodwill				$ 74
NAKAN [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 249
Cash	10
Accounts receivable	53
Inventories	40
Prepaid expenses and other current assets	7
Property, plant and equipment	75
Operating lease right-of-use assets	3
Other assets	12
Total assets acquired	330
Accounts and notes payable	57
Accrued and other liabilities	18
Deferred income taxes	31
Pension and other post-retirement benefits	4
Operating lease liabilities	3
Other long-term liabilities	8
Total liabilities assumed	121
Total identifiable net assets acquired	209
Goodwill	40
Total purchase consideration	249
NAKAN [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Intangible assets	65
NAKAN [Member] | Technology-Based Intangible Assets [Member]
Business Acquisition [Line Items]
Intangible assets	40
NAKAN [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Intangible assets	$ 25

Commitments and Contingencies_2

Commitments and Contingencies (Additional Information) (Detail) - USD ($) $ in Millions	May 22, 2019	Jun. 18, 2018	May 31, 2017	Jun. 30, 2019	Dec. 31, 2018
Environmental Loss Contingencies [Line Items]
Document Period End Date				Jun. 30, 2019
Environmental Loss contingency accrual				$ 49	$ 54
Site Contingency, Percentage of Cost Potentially of Other Responsible Parties [Line Items]				100.00%
PolyOne [Member]
Environmental Loss Contingencies [Line Items]
Site Contingency, Percentage of Cost Potentially of Other Responsible Parties [Line Items]	100.00%
PolyOne [Member] | Pending Litigation [Member]
Environmental Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value			$ 11
Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss				$ 65
Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Reasonably Possible Additional Loss				130
Environmental Protection Agency [Member] | Operation and Maintenance [Member]
Environmental Loss Contingencies [Line Items]
Environmental Remediation Expense		$ 107
Environmental Protection Agency [Member] | Operation and Maintenance [Member] | Minimum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost				1
Environmental Protection Agency [Member] | Operation and Maintenance [Member] | Maximum [Member]
Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost				$ 3

Segment Information (Additional

Segment Information (Additional Information) (Detail)	6 Months Ended
	Jun. 30, 2019Segment
Segment Reporting [Abstract]
Number of segments	2

Segment Information (Segment Re

Segment Information (Segment Reporting Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Net sales	$ 2,144	$ 2,235	$ 4,169	$ 4,385
Income (loss) from operations	194	404	328	805
Depreciation and amortization	176	156	347	312
Other income (expense), net	2	8	11	30
Provision for (benefit from) income taxes	39	93	70	182
Additions to property, plant and equipment	208	158	411	312
Operating Segments [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	477	482	936	985
Income (loss) from operations	82	158	119	321
Depreciation and amortization	36	33	71	67
Other income (expense), net	1	1	3	3
Provision for (benefit from) income taxes	18	36	27	73
Additions to property, plant and equipment	37	26	62	48
Operating Segments [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,667	1,753	3,233	3,400
Income (loss) from operations	129	271	230	537
Depreciation and amortization	138	120	272	238
Other income (expense), net	2	4	6	16
Provision for (benefit from) income taxes	22	69	45	130
Additions to property, plant and equipment	169	128	346	258
Operating Segments [Member] | Polyethylene [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	345	387	682	756
Operating Segments [Member] | Styrene, Feedstock And Other [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	132	95	254	229
Operating Segments [Member] | PVC, Caustic Soda And Other [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	1,319	1,396	2,626	2,754
Operating Segments [Member] | Building Products [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	348	357	607	646
Corporate and other [Member]
Segment Reporting Information [Line Items]
Income (loss) from operations	(17)	(25)	(21)	(53)
Depreciation and amortization	2	3	4	7
Other income (expense), net	(1)	3	2	11
Provision for (benefit from) income taxes	(1)	(12)	(2)	(21)
Additions to property, plant and equipment	2	4	3	6
Intersegment sales [Member]
Segment Reporting Information [Line Items]
Net sales	75	113	167	233
Intersegment sales [Member] | Olefins [Member]
Segment Reporting Information [Line Items]
Net sales	74	112	166	232
Intersegment sales [Member] | Vinyls [Member]
Segment Reporting Information [Line Items]
Net sales	$ 1	$ 1	$ 1	$ 1

Segment Information (Reconcilia

Segment Information (Reconciliation of Total Segment Income from Operations to Consolidated Income before Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting [Abstract]
Income from operations	$ 194	$ 404	$ 328	$ 805
Interest expense	(28)	(31)	(58)	(68)
Other income (expense), net	2	8	11	30
Income before income taxes	$ 168	$ 381	$ 281	$ 767

Segment Information (Total Asse

Segment Information (Total Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 12,216	$ 11,602
Operating Segments [Member] | Olefins [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,057	2,024
Operating Segments [Member] | Vinyls [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	9,766	8,879
Corporate and other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 393	$ 699

Westlake Chemical Partners LP_2

Westlake Chemical Partners LP (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 29, 2019	Jun. 30, 2019	Dec. 31, 2014
Related Party Transaction [Line Items]
Partners' Capital Account, Units, Sold in Public Offering			12,937,500
Partners' Capital Account, Units, Sold in Private Placement	2,940,818
Sale of Unit Price Per Unit	$ 21.40
Proceeds from Issuance of Private Placement	$ 63
Westlake Chemical OpCo LP [Member]
Related Party Transaction [Line Items]
Proceeds from issuance of Westlake Chemical Partners LP common units	$ 201
Limited Partner [Member] | Westlake Chemical OpCo LP [Member]
Related Party Transaction [Line Items]
Limited Partnership Ownership Percentage Increase	4.50%
Principal Stockholder [Member] | TTWF LP [Member]
Related Party Transaction [Line Items]
Partners' Capital Account, Units, Acquisitions	1,401,869
Subsidiary of Common Parent [Member] | Limited Partner [Member] | Westlake Chemical OpCo LP [Member]
Related Party Transaction [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest		22.80%
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		77.20%
Subsidiary of Common Parent [Member] | Limited Partner [Member] | Westlake Chemical Partners LP [Member]
Related Party Transaction [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest		40.10%
Ownership interest (in units)		14,122,230

Subsequent Event (Details)

Subsequent Event (Details) € in Millions, $ in Millions	Jul. 17, 2019USD ($)	Jul. 17, 2019EUR (€)	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Subsequent Event [Line Items]
Long-term Debt			$ 2,669	$ 2,668
Senior Notes [Member] | One Point Six Two Five Percentage Senior Notes Due Twenty Twenty Nine [Member] [Domain] | Subsequent Event [Member]
Subsequent Event [Line Items]
Debt Instrument, Face Amount | €		€ 700
Stated interest rate (percent)	1.625%	1.625%
Long-term Debt	$ 779