Revenue Recognition - Disaggregation of net sales (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2025		Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Net sales		$ 2,419		$ 2,648		$ 7,340		$ 7,910
Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		1,384		1,481		4,113		4,326
Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales	[1]	1,035		1,167		3,227		3,584
Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Net sales		(26)	[2]	(23)	[2]	(65)	[3]	(69)	[3]
Intersegment Eliminations | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		26		23		65		69
North America | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		378		419		1,131		1,211
North America | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		363		374		1,113		1,152
Europe and Africa | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		404		414		1,210		1,313
Europe and Africa | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		373		406		1,162		1,250
Asia-Pacific | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		568		610		1,670		1,693
Asia-Pacific | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		275		355		876		1,095
South America | Engineered Materials
Disaggregation of Revenue [Line Items]
Net sales		34		38		102		109
South America | Acetyl Chain
Disaggregation of Revenue [Line Items]
Net sales		$ 24		$ 32		$ 76		$ 87

[1] Excludes intersegment sales of $26 million and $23 million for the three months ended September 30, 2025 and 2024, respectively. Excludes intersegment sales of $65 million and $69 million for the nine months ended September 30, 2025 and 2024, respectively.

[2] Includes intersegment sales primarily related to the Acetyl Chain.

[3] Includes intersegment sales primarily related to the Acetyl Chain.