Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025
Retirement-Related Benefits
Total plan contributions	$ 209	$ 179
Trust for Benefit of Employees
Retirement-Related Benefits
Contributions by employer - noncash	648	580
U.S. nonpension postretirement benefit plan
Retirement-Related Benefits
Total plan contributions	187	159
Non-U.S. DB plans and multi-employer plans
Retirement-Related Benefits
Total plan contributions	$ 22	$ 21