Segment and Geographic Area Information - Disaggregation of Revenue by Major End Market Served (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue, Major Customer [Line Items]
Sales	$ 1,238	$ 1,134	$ 1,253	$ 1,634	$ 1,734	$ 1,794	$ 1,818	$ 1,752	$ 5,259	$ 7,098	$ 6,778
Third-party sales
Revenue, Major Customer [Line Items]
Sales									5,257	7,105	6,798
Third-party sales | Engine Products
Revenue, Major Customer [Line Items]
Sales									2,406	3,320	3,092
Third-party sales | Fastening Systems
Revenue, Major Customer [Line Items]
Sales									1,245	1,561	1,531
Third-party sales | Engineered Structures
Revenue, Major Customer [Line Items]
Sales									927	1,255	1,209
Third-party sales | Forged Wheels
Revenue, Major Customer [Line Items]
Sales									679	969	966
Third-party sales | Aerospace - Commercial
Revenue, Major Customer [Line Items]
Sales									2,597	4,186	3,996
Third-party sales | Aerospace - Commercial | Engine Products
Revenue, Major Customer [Line Items]
Sales									1,247	2,229	2,056
Third-party sales | Aerospace - Commercial | Fastening Systems
Revenue, Major Customer [Line Items]
Sales									808	1,060	1,069
Third-party sales | Aerospace - Commercial | Engineered Structures
Revenue, Major Customer [Line Items]
Sales									542	897	871
Third-party sales | Aerospace - Commercial | Forged Wheels
Revenue, Major Customer [Line Items]
Sales									0	0	0
Third-party sales | Aerospace - Defense
Revenue, Major Customer [Line Items]
Sales									1,016	889	726
Third-party sales | Aerospace - Defense | Engine Products
Revenue, Major Customer [Line Items]
Sales									557	475	373
Third-party sales | Aerospace - Defense | Fastening Systems
Revenue, Major Customer [Line Items]
Sales									156	158	120
Third-party sales | Aerospace - Defense | Engineered Structures
Revenue, Major Customer [Line Items]
Sales									303	256	233
Third-party sales | Aerospace - Defense | Forged Wheels
Revenue, Major Customer [Line Items]
Sales									0	0	0
Third-party sales | Commercial Transportation
Revenue, Major Customer [Line Items]
Sales									834	1,217	1,246
Third-party sales | Commercial Transportation | Engine Products
Revenue, Major Customer [Line Items]
Sales									0	20	48
Third-party sales | Commercial Transportation | Fastening Systems
Revenue, Major Customer [Line Items]
Sales									155	227	229
Third-party sales | Commercial Transportation | Engineered Structures
Revenue, Major Customer [Line Items]
Sales									0	0	0
Third-party sales | Commercial Transportation | Forged Wheels
Revenue, Major Customer [Line Items]
Sales									679	970	969
Third-party sales | Industrial and Other
Revenue, Major Customer [Line Items]
Sales									810	813	830
Third-party sales | Industrial and Other | Engine Products
Revenue, Major Customer [Line Items]
Sales									602	596	615
Third-party sales | Industrial and Other | Fastening Systems
Revenue, Major Customer [Line Items]
Sales									126	116	113
Third-party sales | Industrial and Other | Engineered Structures
Revenue, Major Customer [Line Items]
Sales									82	102	105
Third-party sales | Industrial and Other | Forged Wheels
Revenue, Major Customer [Line Items]
Sales									$ 0	$ (1)	$ (3)