Unaudited Interim Consolidated Statement Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balance as of the beginning of the period, shares at Dec. 31, 2019		119,555,207	49,417,965
Total Celanese Corporation stockholders' equity at Dec. 31, 2019		$ 0	$ (3,846)	$ 254	$ 6,399	$ (300)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation, net of tax				(12)
Stock awards, shares		383,122
Stock awards		$ 0
Purchases of treasury stock, shares	(1,709,431)	(1,709,431)	1,709,431
Purchases of treasury stock, including related fees	$ (150)	$ 0	$ (150)
Net earnings (loss) attributable to Celanese Corporation	218				218
Common stock dividends					(74)
Other comprehensive income (loss), net of tax	(41)					(41)
Balance as of the end of the period, shares at Mar. 31, 2020		118,228,898	51,127,396
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2019							$ 391
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	2						2
(Distributions to) contributions from noncontrolling interests							(5)
Stockholders' Equity Attributable to Noncontrolling Interest at Mar. 31, 2020							388
Total Celanese Corporation stockholders' equity at Mar. 31, 2020	2,448	$ 0	$ (3,996)	242	6,543	(341)
Balance as of the end of the period at Mar. 31, 2020	2,836
Balance as of the beginning of the period, shares at Dec. 31, 2020		114,168,464	55,234,515
Balance as of the beginning of the period at Dec. 31, 2020	3,895
Total Celanese Corporation stockholders' equity at Dec. 31, 2020	$ 3,526	$ 0	$ (4,494)	257	8,091	(328)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation, net of tax				(4)
Stock awards, shares		296,090
Stock awards		$ 0
Purchases of treasury stock, shares	(1,831,970)	(1,831,970)	1,831,970
Purchases of treasury stock, including related fees	$ (250)	$ 0	$ (250)
Net earnings (loss) attributable to Celanese Corporation	322				322
Common stock dividends					(78)
Other comprehensive income (loss), net of tax	26					26
Balance as of the end of the period, shares at Mar. 31, 2021		112,632,584	57,066,485
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2020	369						369
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	1						1
(Distributions to) contributions from noncontrolling interests							(5)
Stockholders' Equity Attributable to Noncontrolling Interest at Mar. 31, 2021	365						$ 365
Total Celanese Corporation stockholders' equity at Mar. 31, 2021	3,542	$ 0	$ (4,744)	$ 253	$ 8,335	$ (302)
Balance as of the end of the period at Mar. 31, 2021	$ 3,907