Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net income	$ 1,339	$ 420	$ 665
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization	601	378	246
Stock-based compensation expense	23	14	10
Gains realized on previously held shares of Axiall common stock and from sales of securities	0	(54)	(4)
Gain on acquisition, net of loss on the fair value remeasurement of preexisting equity interest	0	0	(21)
Loss from disposition of property, plant and equipment	22	9	11
Deferred income taxes	(534)	101	40
Other losses, net	(3)	5	6
Changes in operating assets and liabilities, net of effect of business acquisitions
Accounts receivable	(40)	50	63
Inventories	(32)	(62)	99
Prepaid expenses and other current assets	26	11	(4)
Accounts payable	86	12	(22)
Accrued liabilities	115	48	(8)
Other, net	(65)	(98)	(2)
Net cash provided by operating activities	1,538	834	1,079
Cash flows from investing activities
Acquisition of business, net of cash acquired	(13)	(2,438)	16
Additions to property, plant and equipment	(577)	(629)	(491)
Additions to cost method investment	(66)	(17)	0
Proceeds from disposition of equity method investment	0	0	28
Proceeds from sales and maturities of securities	0	663	49
Purchase of securities	0	(138)	(605)
Other	4	(4)	(3)
Net cash used for investing activities	(652)	(2,563)	(1,006)
Cash flows from financing activities
Debt issuance costs	(6)	(36)	0
Dividends paid	(103)	(97)	(92)
Distributions to noncontrolling interests	(28)	(17)	(15)
Proceeds from debt issuance and drawdown of revolver	233	608	53
Net proceeds from issuance of Westlake Chemical Partners LP common units	111	0	0
Proceeds from senior notes issuance	745	1,429	0
Repayment of term loan	(150)	0	0
Restricted cash associated with term loan	154	(154)	0
Repayment of revolver	(550)	(125)	0
Repayment of notes payable	(257)	(13)	(74)
Repurchase of common stock for treasury	0	(67)	(163)
Other	11	5	4
Net cash provided by (used for) financing activities	160	1,533	(287)
Effect of exchange rate changes on cash and cash equivalents	26	(8)	(4)
Net increase (decrease) in cash and cash equivalents	1,072	(204)	(218)
Cash and cash equivalents at beginning of the year	459	663	881
Cash and cash equivalents at end of the year	$ 1,531	$ 459	$ 663