Earnings (Loss) and Dividends per Share (Schedule of Net Income Attributable to Common Stockholders) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Earnings and Dividends Per Share [Abstract]
Net income (loss) attributable to Westlake Corporation	$ 260	$ (142)	$ 91	$ (182)
Net income (loss) attributable to participating securities	1	(1)	0	(1)
Net income (loss) attributable to common stockholders	$ 259	$ (141)	$ 91	$ (181)

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details