Restructuring and Other Charges - 2020 Actions (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($) employee position	Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		$ 182	$ 582	$ 163
Benefit from termination of plan		3
Curtailment benefit				(9)
Impairment of assets to be disposed of		5
Accelerated depreciation		2
Gain (loss) on sale of assets		3	1
Pension benefits paid
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		69
Settlement		(76)	(9)	(96)
Curtailment benefit		0	0	(23)
Other postretirement benefits
Restructuring Cost and Reserve [Line Items]
Settlement		0	0	0
Curtailment benefit	$ (9)	2	58	$ 28
Layoff costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		$ 113	$ 69
Number of employees associated with layoff costs | employee		4,301	917
Layoff costs | Pension benefits paid
Restructuring Cost and Reserve [Line Items]
Settlement		$ (74)
Layoff costs | Engine Products
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		1,706	103	34
Layoff costs | Fastening Systems
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		1,675	132	55
Layoff costs | Engineered Structures
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		805	128
Layoff costs | Forged Wheels
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		92	60
Layoff costs | Corporate
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		23	494	36
U.K. and U.S. pension plan settlement accounting | Pension benefits paid
Restructuring Cost and Reserve [Line Items]
Settlement		$ 74
Facility Closing
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		6		$ 9
Facility Closing | U.K. Forging Business
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		5
Impairment Of A Cost Method Investment
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		5	$ 5
Asset Impairment Associated Facility Closure
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		1
Reversal Of Prior Period Programs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges (E)		$ (21)	$ (6)	$ (8)
Restructuring Programs Layoffs Two Thousand Twenty
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | position		4,301
Approximate number of employees already laid off | position		3,519