Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement-Related Benefits
Employer contributions	$ 94	$ 66	$ 311	$ 355
Pension Plans, including Multi-employer Plans, and Nonpension Postretirement Benefits Plans
Retirement-Related Benefits
Contributions by employer - Noncash	155	101	410	357
U.S.
Retirement-Related Benefits
Employer contributions	65	33	200	227
Non-U.S.
Retirement-Related Benefits
Employer contributions	$ 29	$ 34	$ 111	$ 128