Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Retirement-Related Benefits
Defined benefit and contribution pension plans - cost	$ 456	$ 600	$ 934	$ 1,219
Nonpension postretirement plans - cost	33	44	66	88
Total	$ 489	$ 644	$ 1,000	$ 1,307
Year-to-year percent change, defined benefit and contribution pension plans cost (as a percent)	(24.00%)		(23.40%)
Year-to-year percent change, nonpension postretirement plans cost (as a percent)	(25.00%)		(25.00%)
Year-to-year percent change, total (as a percent)	(24.10%)		(23.50%)