Intangible Assets Including Goodwill - Intangible Assets Activity (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Intangible assets
Intangible assets, increase (decrease)			$ (771)
Intangible asset amortization expense	$ 646	$ 613	1,897	$ 1,858
Retirement of fully amortized intangible assets			$ 581

The aggregate expense net of any currency impact charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

No definition available.

Name:	ibm_AmortizationOfIntangibleAssetsNetOfCurrencyImpact
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration