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, 2018		128,095,849	40,323,105
Total Celanese Corporation stockholders' equity at Dec. 31, 2018		$ 0	$ (2,849)	$ 233	$ 5,847	$ (247)
Stock option exercises, shares		14,045
Stock-based compensation, net of tax				12
Stock option exercises		$ 0		(1)
Stock awards, shares		557,842
Stock awards		$ 0
Purchases of treasury stock, shares	(7,334,433)	(7,334,433)	7,334,433
Purchases of treasury stock, including related fees	$ (775)	$ 0	$ (775)
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture			(42,778)
Stock-based compensation, net of tax			$ 2
Net earnings (loss) attributable to Celanese Corporation	809				809
Common stock dividends					(225)
Other comprehensive income (loss), net of tax	(59)					(59)
Balance as of the end of the period, shares at Sep. 30, 2019		121,333,303	47,614,760
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2018							$ 395
Net earnings (loss) attributable to noncontrolling interests	4						4
(Distributions to) contributions from noncontrolling interests							(7)
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2019							392
Total Celanese Corporation stockholders' equity at Sep. 30, 2019	2,747	$ 0	$ (3,622)	244	6,431	(306)
Balance as of the end of the period at Sep. 30, 2019	3,139
Balance as of the beginning of the period, shares at Jun. 30, 2019		123,740,349	45,170,482
Total Celanese Corporation stockholders' equity at Jun. 30, 2019		$ 0	$ (3,347)	233	6,245	(267)
Stock-based compensation, net of tax				11
Stock awards, shares		37,232
Stock awards		$ 0
Purchases of treasury stock, shares		(2,444,278)	2,444,278
Purchases of treasury stock, including related fees		$ 0	$ (275)
Net earnings (loss) attributable to Celanese Corporation	263				263
Common stock dividends					(77)
Other comprehensive income (loss), net of tax	(39)					(39)
Balance as of the end of the period, shares at Sep. 30, 2019		121,333,303	47,614,760
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2019							390
Net earnings (loss) attributable to noncontrolling interests	2						2
(Distributions to) contributions from noncontrolling interests							0
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2019							392
Total Celanese Corporation stockholders' equity at Sep. 30, 2019	2,747	$ 0	$ (3,622)	244	6,431	(306)
Balance as of the end of the period at Sep. 30, 2019	3,139
Balance as of the beginning of the period, shares at Dec. 31, 2019		119,555,207	49,417,965
Balance as of the beginning of the period at Dec. 31, 2019	2,898
Total Celanese Corporation stockholders' equity at Dec. 31, 2019	$ 2,507	$ 0	$ (3,846)	254	6,399	(300)
Stock option exercises, shares		0
Stock-based compensation, net of tax				(6)
Stock option exercises		$ 0		0
Stock awards, shares		444,903
Stock awards		$ 0
Purchases of treasury stock, shares	(2,770,321)	(2,770,321)	2,770,321
Purchases of treasury stock, including related fees	$ (261)	$ 0	$ (261)
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	532				532
Common stock dividends					(221)
Other comprehensive income (loss), net of tax	(44)					(44)
Balance as of the end of the period, shares at Sep. 30, 2020		117,229,789	52,143,916
Stockholders' Equity Attributable to Noncontrolling Interest at Dec. 31, 2019	391						391
Net earnings (loss) attributable to noncontrolling interests	6						6
(Distributions to) contributions from noncontrolling interests							(21)
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2020	376						376
Total Celanese Corporation stockholders' equity at Sep. 30, 2020	2,508	$ 0	$ (4,106)	248	6,710	(344)
Balance as of the end of the period at Sep. 30, 2020	2,884
Balance as of the beginning of the period, shares at Jun. 30, 2020		118,288,296	51,083,026
Total Celanese Corporation stockholders' equity at Jun. 30, 2020		$ 0	$ (3,995)	252	6,576	(346)
Stock-based compensation, net of tax				(4)
Stock awards, shares		2,383
Stock awards		$ 0
Purchases of treasury stock, shares		(1,060,890)	1,060,890
Purchases of treasury stock, including related fees		$ 0	$ (111)
Net earnings (loss) attributable to Celanese Corporation	207				207
Common stock dividends					(73)
Other comprehensive income (loss), net of tax	2					2
Balance as of the end of the period, shares at Sep. 30, 2020		117,229,789	52,143,916
Stockholders' Equity Attributable to Noncontrolling Interest at Jun. 30, 2020							382
Net earnings (loss) attributable to noncontrolling interests	2						2
(Distributions to) contributions from noncontrolling interests							(8)
Stockholders' Equity Attributable to Noncontrolling Interest at Sep. 30, 2020	376						$ 376
Total Celanese Corporation stockholders' equity at Sep. 30, 2020	2,508	$ 0	$ (4,106)	$ 248	$ 6,710	$ (344)
Balance as of the end of the period at Sep. 30, 2020	$ 2,884