Retirement-Related Benefits - Changes in Benefit Obligation and Plan Assets (Details) - U.S. - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Aug. 31, 2022	Jul. 31, 2022	Dec. 31, 2021
Pension Plans
Changes in benefit obligation
Interest cost	$ 282	$ 277	$ 885	$ 832
Pension Plans | Qualified Plans
Changes in benefit obligation
Benefit obligation, balance at beginning of period			46,457
Interest cost			853
Actuarial losses/(gains)			(6,973)
Benefits paid from trust			(2,376)
Amendments/curtailments/settlements/other			(16,644)
Benefit obligation, balance at end of period	21,316		21,316
Change in plan assets
Fair value of plan assets, balance at beginning of period			51,851
Actual return on plan assets			(5,746)
Benefits paid from trust			(2,376)
Amendments/curtailments/settlements/other			(16,644)
Fair value of plan assets, balance at end of period	27,085		27,085
Funded status	5,769		5,769
Accumulated benefit obligation	21,316		21,316
Discount rate					4.70%		2.60%
Nonpension Postretirement Plans
Changes in benefit obligation
Benefit obligation, balance at beginning of period			3,404
Service cost	1	2	4	5
Interest cost	21	$ 16	58	$ 49
Plan participants' contributions			33
Actuarial losses/(gains)			(624)
Benefits paid from trust			(285)
Direct benefit payments			(2)
Benefit obligation, balance at end of period	2,588		2,588
Change in plan assets
Fair value of plan assets, balance at beginning of period			8
Employer contributions			272
Plan participant's contributions			33
Benefits paid from trust			(285)
Fair value of plan assets, balance at end of period	28		28
Funded status	$ (2,560)		$ (2,560)
Discount rate						4.10%	2.30%