Earnings (Loss) Per Share (Schedule of Earnings (Loss) Per Share) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Amounts attributable to Celanese Corporation
Earnings (loss) from continuing operations		$ 209	$ 268	$ 544	$ 816
Earnings (loss) from discontinued operations		(2)	(5)	(12)	(7)
Net earnings (loss)		$ 207	$ 263	$ 532	$ 809
Weighted average shares - basic		118,045,476	122,699,859	118,543,853	125,159,647
Incremental shares attributable to equity awards(1)	[1]	519,344	599,805	575,350	709,182
Weighted average shares - diluted		118,564,820	123,299,664	119,119,203	125,868,829

[1] Excludes 492 and 0 equity award shares for the three months ended September 30, 2020 and 2019, respectively, as their effect would have been antidilutive. Excludes 8,127 and 0 equity award shares for the nine months ended September 30, 2020 and 2019, respectively, as their effect would have been antidilutive.