Restructuring and Other Charges - 2019 Actions (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($) employee	Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($) employee
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 182	$ 582	$ 163
Business exit costs			7
Gain (loss) on sale of assets		3	1
Non-cash asset impairments (O)		5	442	$ 9
Impairment Of Disks
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges	$ 428		428
Employee Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 113	$ 69
Number of employees associated with layoff costs | employee		4,301	917
Employee Severance | Corporate
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		23	494	36
UK Forgings
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			$ 46
Impairment For Trade Name Intangible Asset And Fixed Assets
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			14
Small Additive Business
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			13
Corporate Aircraft
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			12
Pension Settlement Cost
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 8	9	$ 96
Special Termination Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			2
Employee Severance Life Insurance Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			16
Reversal Of Prior Period Programs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		(21)	(6)	$ (8)
Impairment Of A Cost Method Investment
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges		$ 5	5
Engine Products | Disks Long Lived Asset Group
Restructuring Cost and Reserve [Line Items]
Non-cash asset impairments (O)			$ 247
Engine Products | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		1,706	103	34
Engineered Structures | Disks Long Lived Asset Group
Restructuring Cost and Reserve [Line Items]
Non-cash asset impairments (O)			$ 181
Engineered Structures | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		805	128
Fastening Systems | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		1,675	132	55
Forged Wheels | Employee Severance
Restructuring Cost and Reserve [Line Items]
Number of employees associated with layoff costs | employee		92	60