Earnings (Loss) and Dividends per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Earnings and Dividends Per Share [Abstract]
Weighted average common shares—basic (in shares)	127,830,227	128,251,427	127,953,601	128,265,950
Assumed exercise of options and vesting of performance stock units (in shares)	132,303	0	317,223	0
Weighted average common shares—diluted (in shares)	127,962,530	128,251,427	128,270,824	128,265,950
Earnings (loss) per common share attributable to Westlake Corporation:
Basic (in dollars per share)	$ 0.05	$ (6.06)	$ 0.75	$ (7.48)
Diluted (in dollars per share)	$ 0.05	$ (6.06)	$ 0.75	$ (7.48)

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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