Retirement-Related Benefits - Contributions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Retirement-Related Benefits
Total plan contributions	$ 90	$ 70
Trust for Benefit of Employees
Retirement-Related Benefits
Contributions by employer - noncash	205	215
U.S. nonpension postretirement benefit plan
Retirement-Related Benefits
Total plan contributions	70	70
Non-U.S. DB plans and multi-employer plans
Retirement-Related Benefits
Total plan contributions	$ 19	$ 1