Segment Information - Disaggregation of Revenue by Major End Market Served (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Major Customer [Line Items]
Sales:	$ 1,134	$ 1,794	$ 4,021	$ 5,364
Third-party sales
Revenue, Major Customer [Line Items]
Sales:	1,134	1,794	4,019	5,372
Third-party sales | Engine Products
Revenue, Major Customer [Line Items]
Sales:	485	844	1,851	2,492
Third-party sales | Fastening Systems
Revenue, Major Customer [Line Items]
Sales:	271	391	982	1,185
Third-party sales | Engineered Structures
Revenue, Major Customer [Line Items]
Sales:	206	318	710	943
Third-party sales | Forged Wheels
Revenue, Major Customer [Line Items]
Sales:	172	241	476	752
Third-party sales | Aerospace - Commercial
Revenue, Major Customer [Line Items]
Sales:	472	1,064	2,100	3,164
Third-party sales | Aerospace - Commercial | Engine Products
Revenue, Major Customer [Line Items]
Sales:	199	571	1,018	1,689
Third-party sales | Aerospace - Commercial | Fastening Systems
Revenue, Major Customer [Line Items]
Sales:	169	267	650	803
Third-party sales | Aerospace - Commercial | Engineered Structures
Revenue, Major Customer [Line Items]
Sales:	104	226	432	672
Third-party sales | Aerospace - Commercial | Forged Wheels
Revenue, Major Customer [Line Items]
Sales:	0	0	0	0
Third-party sales | Aerospace - Defense
Revenue, Major Customer [Line Items]
Sales:	261	226	730	659
Third-party sales | Aerospace - Defense | Engine Products
Revenue, Major Customer [Line Items]
Sales:	142	120	394	350
Third-party sales | Aerospace - Defense | Fastening Systems
Revenue, Major Customer [Line Items]
Sales:	37	41	120	115
Third-party sales | Aerospace - Defense | Engineered Structures
Revenue, Major Customer [Line Items]
Sales:	82	65	216	194
Third-party sales | Aerospace - Defense | Forged Wheels
Revenue, Major Customer [Line Items]
Sales:	0	0	0	0
Third-party sales | Commercial Transportation
Revenue, Major Customer [Line Items]
Sales:	210	305	594	950
Third-party sales | Commercial Transportation | Engine Products
Revenue, Major Customer [Line Items]
Sales:	0	5	0	17
Third-party sales | Commercial Transportation | Fastening Systems
Revenue, Major Customer [Line Items]
Sales:	38	59	118	179
Third-party sales | Commercial Transportation | Engineered Structures
Revenue, Major Customer [Line Items]
Sales:	0	0	0	0
Third-party sales | Commercial Transportation | Forged Wheels
Revenue, Major Customer [Line Items]
Sales:	172	241	476	754
Third-party sales | Industrial and Other
Revenue, Major Customer [Line Items]
Sales:	191	199	595	599
Third-party sales | Industrial and Other | Engine Products
Revenue, Major Customer [Line Items]
Sales:	144	148	439	436
Third-party sales | Industrial and Other | Fastening Systems
Revenue, Major Customer [Line Items]
Sales:	27	24	94	88
Third-party sales | Industrial and Other | Engineered Structures
Revenue, Major Customer [Line Items]
Sales:	20	27	62	77
Third-party sales | Industrial and Other | Forged Wheels
Revenue, Major Customer [Line Items]
Sales:	$ 0	$ 0	$ 0	$ (2)