Earnings (Loss) Per Share (Schedule of Earnings (Loss) Per Share) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amounts attributable to Celanese Corporation
Earnings (loss) from continuing operations		$ 519	$ 209	$ 1,384	$ 544
Earnings (loss) from discontinued operations		(13)	(2)	(18)	(12)
Net earnings (loss)		$ 506	$ 207	$ 1,366	$ 532
Weighted average shares - basic		110,532,051	118,045,476	112,101,651	118,543,853
Incremental shares attributable to equity awards(1)	[1]	512,507	519,344	597,646	575,350
Weighted average shares - diluted		111,044,558	118,564,820	112,699,297	119,119,203

[1] There were no antidilutive equity award shares excluded for the three months ended September 30, 2021 and 2020. There were 67 and 8,127 equity award shares excluded for the nine months ended September 30, 2021 and 2020, respectively, as their effect would have been antidilutive.