Intangible Assets Including Goodwill - Intangible Assets Activity (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Intangible assets
Intangible assets, increase (decrease)	$ (261)
Intangible asset amortization expense	620	$ 622
Retirement of fully amortized intangible assets	$ 256

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