Earnings (Loss) Per Share - Schedule of Earnings (Loss) Per Share (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2026		Sep. 30, 2025		Sep. 30, 2026	Sep. 30, 2025
Amounts attributable to Celanese Corporation
Earnings (loss) from continuing operations	$ 75		$ (1,357)		$ 247	$ (1,169)
Earnings (loss) from discontinued operations	(1)		0		(4)	(15)
Net earnings (loss)	$ 74		$ (1,357)		$ 243	$ (1,184)
Weighted average shares - basic (in shares)	109,820,213		109,565,996		109,753,986	109,504,912
Incremental shares attributable to equity awards(1)	380,621	[1]	0	[1]	378,708	0
Weighted average shares - diluted	110,200,834		109,565,996		110,132,694	109,504,912
Antidilutive securities excluded from computation of earnings per share, amount			231,627			222,970

[1] Excludes anti-dilutive incremental shares attributable to equity awards as follows: Three Months Ended
September 30, Nine Months Ended
September 30, 2026202520262025(In shares )Options to purchase shares of Common Stock989,102 731,008 938,906 671,183 Equity award shares40,729 57,590 25,470 67,716