Unaudited Interim Consolidated Statement Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock, Common	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net
Balance as of the beginning of the period (in shares) at Dec. 31, 2023			61,570,314
Balance as of the beginning of the period (in shares) at Dec. 31, 2023		108,906,426
Balance as of the beginning of the period at Dec. 31, 2023		$ 0	$ (5,488)	$ 394	$ 12,903	$ (744)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises, shares		10,088
Stock option exercises		$ 0		1
Stock awards (in shares)		349,854
Stock awards		$ 0
Issuance of treasury stock under stock plans (in shares)			(33,068)
Issuance of treasury stock under stock plans			$ 1
Stock-based compensation, net of tax				2
Net earnings (loss) attributable to Celanese Corporation	$ 383				383
Common stock dividends					(230)
Other comprehensive income (loss), net of tax	20					17
Balance as of the end of the period (in shares) at Sep. 30, 2024		109,266,368
Balance as of the end of the period at Sep. 30, 2024	7,239	$ 0	$ (5,487)	397	13,056	(727)
Balance as of the end of the period (in shares) at Sep. 30, 2024			61,537,246
Balance as of the beginning of the period, noncontrolling interest at Dec. 31, 2023	461
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	5
Other comprehensive income (loss), net of tax	3
Distributions/dividends to noncontrolling interests	(25)
Balance as of the end of the period, noncontrolling interest at Sep. 30, 2024	444
Balance as of the beginning of the period (in shares) at Dec. 31, 2023			61,570,314
Balance as of the beginning of the period (in shares) at Dec. 31, 2023		108,906,426
Balance as of the beginning of the period at Dec. 31, 2023		$ 0	$ (5,488)	394	12,903	(744)
Balance as of the end of the period (in shares) at Dec. 31, 2024		109,327,556
Balance as of the end of the period at Dec. 31, 2024	$ 5,129	$ 0	$ (5,486)	409	11,054	(848)
Balance as of the end of the period (in shares) at Dec. 31, 2024	61,499,640		61,499,640
Balance as of the beginning of the period, noncontrolling interest at Dec. 31, 2023	$ 461
Balance as of the end of the period, noncontrolling interest at Dec. 31, 2024	434
Balance as of the beginning of the period (in shares) at Jun. 30, 2024			61,537,246
Balance as of the beginning of the period (in shares) at Jun. 30, 2024		109,262,563
Balance as of the beginning of the period at Jun. 30, 2024		$ 0	$ (5,487)	394	13,019	(792)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises, shares		849
Stock option exercises		$ 0
Stock awards (in shares)		2,956
Stock awards		$ 0
Issuance of treasury stock under stock plans (in shares)			0
Issuance of treasury stock under stock plans			$ 0
Stock-based compensation, net of tax				3
Net earnings (loss) attributable to Celanese Corporation	113				113
Common stock dividends					(76)
Other comprehensive income (loss), net of tax	69					65
Balance as of the end of the period (in shares) at Sep. 30, 2024		109,266,368
Balance as of the end of the period at Sep. 30, 2024	7,239	$ 0	$ (5,487)	397	13,056	(727)
Balance as of the end of the period (in shares) at Sep. 30, 2024			61,537,246
Balance as of the beginning of the period, noncontrolling interest at Jun. 30, 2024	443
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	4
Other comprehensive income (loss), net of tax	4
Distributions/dividends to noncontrolling interests	(7)
Balance as of the end of the period, noncontrolling interest at Sep. 30, 2024	444
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	7,683
Total equity	$ 5,563					(848)
Balance as of the beginning of the period (in shares) at Dec. 31, 2024	61,499,640		61,499,640
Balance as of the beginning of the period (in shares) at Dec. 31, 2024		109,327,556
Balance as of the beginning of the period at Dec. 31, 2024	$ 5,129	$ 0	$ (5,486)	409	11,054	(848)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises, shares		0
Stock option exercises		$ 0		0
Stock awards (in shares)		176,799
Stock awards		$ 0
Issuance of treasury stock under stock plans (in shares)			(87,055)
Issuance of treasury stock under stock plans			$ 3
Stock-based compensation, net of tax				16
Net earnings (loss) attributable to Celanese Corporation	(1,184)				(1,184)
Common stock dividends					(9)
Other comprehensive income (loss), net of tax	1					(1)
Balance as of the end of the period (in shares) at Sep. 30, 2025		109,504,355
Balance as of the end of the period at Sep. 30, 2025	$ 3,954	$ 0	$ (5,483)	425	9,861	(849)
Balance as of the end of the period (in shares) at Sep. 30, 2025	61,412,585		61,412,585
Balance as of the beginning of the period, noncontrolling interest at Dec. 31, 2024	$ 434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	11
Other comprehensive income (loss), net of tax	2
Distributions/dividends to noncontrolling interests	(22)
Balance as of the end of the period, noncontrolling interest at Sep. 30, 2025	425
Balance as of the beginning of the period (in shares) at Jun. 30, 2025			61,412,585
Balance as of the beginning of the period (in shares) at Jun. 30, 2025		109,501,876
Balance as of the beginning of the period at Jun. 30, 2025		$ 0	$ (5,483)	419	11,221	(903)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock option exercises, shares		0
Stock option exercises		$ 0
Stock awards (in shares)		2,479
Stock awards		$ 0
Issuance of treasury stock under stock plans (in shares)			0
Issuance of treasury stock under stock plans			$ 0
Stock-based compensation, net of tax				6
Net earnings (loss) attributable to Celanese Corporation	(1,357)				(1,357)
Common stock dividends					(3)
Other comprehensive income (loss), net of tax	55					54
Balance as of the end of the period (in shares) at Sep. 30, 2025		109,504,355
Balance as of the end of the period at Sep. 30, 2025	$ 3,954	$ 0	$ (5,483)	$ 425	$ 9,861	(849)
Balance as of the end of the period (in shares) at Sep. 30, 2025	61,412,585		61,412,585
Balance as of the beginning of the period, noncontrolling interest at Jun. 30, 2025	$ 428
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings (loss) attributable to noncontrolling interests	4
Other comprehensive income (loss), net of tax	1
Distributions/dividends to noncontrolling interests	(8)
Balance as of the end of the period, noncontrolling interest at Sep. 30, 2025	425
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total equity	$ 4,379					$ (849)