Consolidated Statements of Equity - USD ($) $ in Millions	Total		Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]	Noncontrolling Interests [Member]
Balance as of the beginning of the period, shares at Dec. 31, 2017			135,769,256	32,387,713
Balance as of the beginning of the period at Dec. 31, 2017								$ 412
Balance as of the beginning of the year at Dec. 31, 2017			$ 0	$ (2,031)	$ 175	$ 4,920	$ (177)
Stock option exercises, net of tax			$ 0		0
Stock option exercises, shares			0
Purchases of treasury stock, shares			(7,935,392)
Purchases of treasury stock			$ 0
Stock awards, shares			261,985
Stock awards			$ 0
Purchases of treasury stock, shares	7,933,692	[1]		7,935,392
Purchases of treasury stock, including related fees	$ (817)			$ (818)
Stock-based compensation, net of tax				0	58
Net earnings (loss) attributable to Celanese Corporation	1,207					1,207
Common stock dividends						(280)
Other comprehensive income (loss), net of tax	(70)						(70)
Balance as of the end of the year at Dec. 31, 2018	2,984		$ 0	$ (2,849)	233	5,847	(247)
Balance as of the end of the period, shares at Dec. 31, 2018			128,095,849	40,323,105
Net earnings (loss) attributable to noncontrolling interests	(6)							6
(Distributions to) contributions from noncontrolling interests								(23)
Balance as of the end of the period at Dec. 31, 2018								395
Total equity at Dec. 31, 2018	$ 3,379
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture				0
Stock option exercises, net of tax			$ 0		(1)
Stock option exercises, shares			14,045
Purchases of treasury stock, shares			(9,166,267)
Purchases of treasury stock			$ 0
Stock awards, shares			611,580
Stock awards			$ 0
Purchases of treasury stock, shares	9,166,267			9,166,267
Purchases of treasury stock, including related fees	$ (1,000)			$ (1,000)
Stock-based compensation, net of tax				3	22
Net earnings (loss) attributable to Celanese Corporation	852					852
Common stock dividends						(300)
Other comprehensive income (loss), net of tax	(53)						(53)
Balance as of the end of the year at Dec. 31, 2019	2,507		$ 0	$ (3,846)	254	6,399	(300)
Balance as of the end of the period, shares at Dec. 31, 2019			119,555,207	49,417,965
Net earnings (loss) attributable to noncontrolling interests	(6)							6
(Distributions to) contributions from noncontrolling interests								(10)
Balance as of the end of the period at Dec. 31, 2019	391							391
Total equity at Dec. 31, 2019	$ 2,898
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture				(71,407)
Stock option exercises, net of tax			$ 0		0
Stock option exercises, shares			0
Purchases of treasury stock, shares			(5,889,073)
Purchases of treasury stock			$ 0
Stock awards, shares			502,330
Stock awards			$ 0
Purchases of treasury stock, shares	5,889,073			5,889,073
Purchases of treasury stock, including related fees	$ (650)			$ (650)
Stock-based compensation, net of tax				2	3
Net earnings (loss) attributable to Celanese Corporation	1,985					1,985
Common stock dividends						(293)
Other comprehensive income (loss), net of tax	(28)						(28)
Balance as of the end of the year at Dec. 31, 2020	3,526		$ 0	$ (4,494)	$ 257	$ 8,091	$ (328)
Balance as of the end of the period, shares at Dec. 31, 2020			114,168,464	55,234,515
Net earnings (loss) attributable to noncontrolling interests	(7)							7
(Distributions to) contributions from noncontrolling interests								(29)
Balance as of the end of the period at Dec. 31, 2020	369							$ 369
Total equity at Dec. 31, 2020	$ 3,895
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture				(72,523)

[1] Excludes 1,700 common shares reacquired pursuant to an employee clawback agreement.