Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			$ 13
Cash payments			(38)
Other			(83)
Restructuring reserve ending balance	$ 58		58
Restructuring and other charges	22	$ 56	166	$ 572
Accelerated depreciation	2	2	2
Settlements	3	4	67	(8)
Benefit from termination of deferred benefit plan	3		3
Impairment of assets to be disposed of			5
Gain (loss) on sale of assets		1	2	1
Other postretirement benefits
Restructuring Reserve [Roll Forward]
Curtailment benefit	2	0	2	58
Pension benefits
Restructuring Reserve [Roll Forward]
Settlements	8	4	72	8
Pension benefits | United Kingdom and United States
Restructuring Reserve [Roll Forward]
Settlements			72
Layoff costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			13
Cash payments			(38)
Other			(67)
Restructuring reserve ending balance	58		58
Restructuring and other charges	17		150	68
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			0
Cash payments			0
Other			(16)
Restructuring reserve ending balance	$ 0		0
Restructuring and other charges			16
Facility closing
Restructuring Reserve [Roll Forward]
Restructuring and other charges			5
Facility closing | U.K. Forging Business
Restructuring Reserve [Roll Forward]
Restructuring and other charges		$ 43	$ 6	$ 43