Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Retirement-Related Benefits
Total plan contributions	$ 103	$ 117
Trust for Benefit of Employees
Retirement-Related Benefits
Contributions by employer - Noncash	210	192
U.S. nonpension postretirement benefit plans
Retirement-Related Benefits
Total plan contributions	89	109
Non-U.S. DB plans and multi-employer plans
Retirement-Related Benefits
Total plan contributions	14	7
Other Postretirement Benefits Plan | U.S. nonpension postretirement benefit plans
Retirement-Related Benefits
Contributions by employer - Noncash	$ 89	$ 109