Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2020
Goodwill [Roll Forward]
Goodwill		$ 4,786,000,000	$ 4,905,000,000
Accumulated impairment losses		(719,000,000)	(719,000,000)
Goodwill (A and P)		4,102,000,000	4,067,000,000	$ 4,186,000,000
Acquisitions and Divestitures (See Note U)				(13,000,000)
Impairment (See Note U)		0	(2,000,000)
Translation and other			37,000,000	4,000,000
Goodwill, Transfers			0	0
Goodwill		4,823,000,000	4,786,000,000	4,905,000,000
Transfer from Engineered Structures to Discontinued Operations (Arconic Corporation)
Goodwill [Roll Forward]
Goodwill, Transfers	$ 110,000,000			(110,000,000)
Engine Products
Goodwill [Roll Forward]
Goodwill		2,883,000,000	2,785,000,000
Accumulated impairment losses		(719,000,000)	(719,000,000)
Goodwill (A and P)		2,171,000,000	2,164,000,000	2,066,000,000	$ 17,000,000
Acquisitions and Divestitures (See Note U)				(13,000,000)
Impairment (See Note U)			0
Translation and other			24,000,000	6,000,000
Goodwill, Transfers			(17,000,000)	105,000,000
Goodwill		2,890,000,000	2,883,000,000	2,785,000,000
Engine Products | Transfer from Engineered Structures to Discontinued Operations (Arconic Corporation)
Goodwill [Roll Forward]
Goodwill, Transfers				0
Fastening Systems
Goodwill [Roll Forward]
Goodwill		1,607,000,000	1,607,000,000
Accumulated impairment losses		0	0
Goodwill (A and P)		1,620,000,000	1,607,000,000	1,607,000,000
Acquisitions and Divestitures (See Note U)				0
Impairment (See Note U)			0
Translation and other			13,000,000	0
Goodwill, Transfers			0	0
Goodwill		1,620,000,000	1,607,000,000	1,607,000,000
Fastening Systems | Transfer from Engineered Structures to Discontinued Operations (Arconic Corporation)
Goodwill [Roll Forward]
Goodwill, Transfers				0
Engineered Structures
Goodwill [Roll Forward]
Goodwill		289,000,000	506,000,000
Accumulated impairment losses		0	0
Goodwill (A and P)		304,000,000	289,000,000	506,000,000
Acquisitions and Divestitures (See Note U)				0
Impairment (See Note U)			(2,000,000)
Translation and other			0	(2,000,000)
Goodwill, Transfers			17,000,000	(105,000,000)
Goodwill		306,000,000	289,000,000	506,000,000
Engineered Structures | Transfer from Engineered Structures to Discontinued Operations (Arconic Corporation)
Goodwill [Roll Forward]
Goodwill, Transfers				(110,000,000)
Forged Wheels
Goodwill [Roll Forward]
Goodwill		7,000,000	7,000,000
Accumulated impairment losses		0	0
Goodwill (A and P)		7,000,000	7,000,000	7,000,000
Acquisitions and Divestitures (See Note U)				0
Impairment (See Note U)			0
Translation and other			0	0
Goodwill, Transfers			0	0
Goodwill		$ 7,000,000	$ 7,000,000	7,000,000
Forged Wheels | Transfer from Engineered Structures to Discontinued Operations (Arconic Corporation)
Goodwill [Roll Forward]
Goodwill, Transfers				$ 0