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				(2)
Stock awards, shares		442,520
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)
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture			(44,370)
Stock-based compensation, net of tax			$ 1
Net earnings (loss) attributable to Celanese Corporation	325				325
Common stock dividends					(148)
Other comprehensive income (loss), net of tax	(46)					(46)
Balance as of the end of the period, shares at Jun. 30, 2020		118,288,296	51,083,026
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	4						4
(Distributions to) contributions from noncontrolling interests							(13)
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2020							382
Total Celanese Corporation stockholders' equity at Jun. 30, 2020	2,487	$ 0	$ (3,995)	252	6,576	(346)
Balance as of the end of the period at Jun. 30, 2020	2,869
Balance as of the beginning of the period, shares at Mar. 31, 2020		118,228,898	51,127,396
Total Celanese Corporation stockholders' equity at Mar. 31, 2020		$ 0	$ (3,996)	242	6,543	(341)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation, net of tax				10
Stock awards, shares		59,398
Stock awards		$ 0
Purchases of treasury stock, shares		0	0
Purchases of treasury stock, including related fees		$ 0	$ 0
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture			(44,370)
Stock-based compensation, net of tax			$ 1
Net earnings (loss) attributable to Celanese Corporation	107				107
Common stock dividends					(74)
Other comprehensive income (loss), net of tax	(5)					(5)
Balance as of the end of the period, shares at Jun. 30, 2020		118,288,296	51,083,026
Stockholders' Equity Attributable to Noncontrolling Interest at Mar. 31, 2020							388
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	2						2
(Distributions to) contributions from noncontrolling interests							(8)
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2020							382
Total Celanese Corporation stockholders' equity at Jun. 30, 2020	2,487	$ 0	$ (3,995)	252	6,576	(346)
Balance as of the end of the period at Jun. 30, 2020	2,869
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				35
Stock awards, shares		341,526
Stock awards		$ 0
Purchases of treasury stock, shares	(3,394,548)	(3,394,548)	3,394,548
Purchases of treasury stock, including related fees	$ (500)	$ 0	$ (500)
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture			(27,186)
Stock-based compensation, net of tax			$ 1
Net earnings (loss) attributable to Celanese Corporation	860				860
Common stock dividends					(154)
Other comprehensive income (loss), net of tax	30					30
Balance as of the end of the period, shares at Jun. 30, 2021		111,115,442	58,601,877
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	3						3
(Distributions to) contributions from noncontrolling interests							(13)
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2021	359						359
Total Celanese Corporation stockholders' equity at Jun. 30, 2021	3,798	$ 0	$ (4,993)	292	8,797	(298)
Balance as of the end of the period at Jun. 30, 2021	4,157
Balance as of the beginning of the period, shares at Mar. 31, 2021		112,632,584	57,066,485
Total Celanese Corporation stockholders' equity at Mar. 31, 2021		$ 0	$ (4,744)	253	8,335	(302)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation, net of tax				39
Stock awards, shares		45,436
Stock awards		$ 0
Purchases of treasury stock, shares		(1,562,578)	1,562,578
Purchases of treasury stock, including related fees		$ 0	$ (250)
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture			(27,186)
Stock-based compensation, net of tax			$ 1
Net earnings (loss) attributable to Celanese Corporation	538				538
Common stock dividends					(76)
Other comprehensive income (loss), net of tax	4					4
Balance as of the end of the period, shares at Jun. 30, 2021		111,115,442	58,601,877
Stockholders' Equity Attributable to Noncontrolling Interest at Mar. 31, 2021							365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	2						2
(Distributions to) contributions from noncontrolling interests							(8)
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2021	359						$ 359
Total Celanese Corporation stockholders' equity at Jun. 30, 2021	3,798	$ 0	$ (4,993)	$ 292	$ 8,797	$ (298)
Balance as of the end of the period at Jun. 30, 2021	$ 4,157