Revenue Recognition - Disaggregation of net sales (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Net sales		$ 2,556	$ 2,419	$ 7,645	$ 7,340
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-10-01
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		3 months		3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		1 year		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		1 year		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2029-01-01
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period		1 year		1 year
Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		$ 1,368	1,384	$ 4,139	4,113
Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales	[1]	1,188	1,035	3,506	3,227
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Net sales		(21)	(26)	(68)	(65)
Intersegment Eliminations | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		0	0	0	0
Intersegment Eliminations | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		21	26	68	65
North America | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		387	378	1,121	1,131
North America | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		403	363	1,182	1,113
Europe and Africa | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		401	404	1,304	1,210
Europe and Africa | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		436	373	1,285	1,162
Asia-Pacific | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		547	568	1,617	1,670
Asia-Pacific | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		316	275	943	876
South America | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		33	34	97	102
South America | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		$ 33	$ 24	$ 96	$ 76

[1] Excludes intersegment sales of $21 million and $26 million for the three months ended September 30, 2026 and 2025, respectively. Excludes intersegment sales of $68 million and $65 million for the nine months ended September 30, 2026 and 2025, respectively.