Retirement-Related Benefits - IBM Non-U.S. Retirement Plan Change (Details) participant in Thousands, $ in Millions		3 Months Ended		9 Months Ended
	Oct. 29, 2024 USD ($) participant	Dec. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Retirement-Related Benefits
Pension settlement charge			$ 2,700	$ 2,725	$ 0
Subsequent Event | Forecast
Retirement-Related Benefits
Pension settlement charge		$ 400
Subsequent Event | IBMC IBM Retirement Plan | Non-U.S. Plans | Pension Plan
Retirement-Related Benefits
Benefit plan obligations transferred from plan	$ 1,200
Number of participants transferred to insurers | participant	6