Earnings (Loss) Per Share (Schedule of Earnings (Loss) Per Share) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Amounts attributable to Celanese Corporation
Earnings (loss) from continuing operations		$ 542	$ 110	$ 865	$ 335
Earnings (loss) from discontinued operations		(4)	(3)	(5)	(10)
Net earnings (loss)		$ 538	$ 107	$ 860	$ 325
Weighted average shares - basic		112,294,274	118,339,872	112,899,459	118,795,780
Incremental shares attributable to equity awards(1)	[1]	464,365	427,761	571,122	581,735
Weighted average shares - diluted		112,758,639	118,767,633	113,470,581	119,377,515

[1] There were no antidilutive equity award shares excluded for the three and six months ended June 30, 2021. There were 120,210 and 89,241 equity award shares excluded for the three and six months ended June 30, 2020, respectively, as their effect would have been antidilutive.