Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Retirement-Related Benefits
Total plan contributions	$ 233	$ 357
U.S. nonpension postretirement benefit plans
Retirement-Related Benefits
Total plan contributions	188	272
Non-U.S. DB plans and multi-employer plans
Retirement-Related Benefits
Total plan contributions	45	85
Pension Plans, Including Multi-employer Plans
Retirement-Related Benefits
Contributions by employer - Noncash	537	366
Other Postretirement Benefits Plan | U.S. nonpension postretirement benefit plans
Retirement-Related Benefits
Contributions by employer - Noncash	$ 188	$ 247