Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Retirement Benefits [Abstract]
Defined benefit and contribution pension plans — cost	$ 259	$ 456	$ 541	$ 934
Nonpension postretirement plans — cost	33	33	65	66
Total	$ 292	$ 489	$ 606	$ 1,000
Year-to-year percent change, defined benefit and contribution pension plans cost (as a percent)	(43.20%)		(42.10%)
Year-to-year percent change, nonpension postretirement plans cost (as a percent)	(2.20%)		(1.90%)
Year-to-year percent change, total (as a percent)	(40.40%)		(39.40%)