Basis of Presentation (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2022 USD ($) contract	Sep. 30, 2021 USD ($)		Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)		Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 03, 2021
Number of annuity contracts entered into by the company relating to the change in PPP | contract	2
Pre-tax pension settlement charge	$ 5,900.0			$ 5,894.0
Pension settlement charge, net of tax	4,400.0
Provision for/(benefit from) income taxes	(1,287.0)	$ (224.0)	[1]	(1,070.0)	$ (282.0)	[1]
Benefit plan obligation and plan assets transferred to insurers	16,000.0
Common Stocks, Including Additional Paid in Capital	58,117.0			58,117.0				$ 57,319.0
Retained earnings	148,611.0			148,611.0				$ 154,209.0
Other (income) and expenses
Noncontrolling interest amounts, net of tax	$ 3.7	$ 5.5		$ 14.2	$ 14.5
Kyndryl Holdings, Inc
Ownership interest by stockholders (in percent)									19.90%
Percentage of retained interest in investment transferred				100.00%
Revision of Prior Period, Reclassification, Adjustment
Common Stocks, Including Additional Paid in Capital							$ 63.0
Retained earnings							$ (63.0)
Kyndryl Holdings, Inc
Total of Kyndryl stock distributed to IBM stockholders of record as of 10/25/2021 (as a percentage)									80.10%
Share conversion ratio									0.2
Kyndryl Holdings, Inc | Kyndryl Holdings, Inc
Total of Kyndryl stock distributed to IBM stockholders of record as of 10/25/2021 (as a percentage)									80.10%

[1] Reclassified to reflect discontinued operations presentation.