Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Retirement-Related Benefits
Total plan contributions	$ 179	$ 208
Trust for Benefit of Employees
Retirement-Related Benefits
Contributions by employer - noncash	580	600
U.S. nonpension postretirement benefit plan
Retirement-Related Benefits
Total plan contributions	159	155
Non-U.S. DB plans and multi-employer plans
Retirement-Related Benefits
Total plan contributions	$ 21	$ 53