Intangible Assets Including Goodwill - Intangible Assets Activity (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Intangible Asset, Goodwill and Other [Abstract]
Intangible assets, increase (decrease)			$ 2,211
Acquired intangibles			3,834
Intangible asset amortization expense	$ 828	$ 699	2,363	$ 2,027
Retirement of fully amortized intangible assets			$ 361

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.

+ Details

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

- Definition

The amount of fully amortized intangible assets that the entity retired during the period.

+ References

No definition available.

+ Details

Name:	ibm_IntangibleAssetsFullyAmortizedRetired
Namespace Prefix:	ibm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase (decrease) in finite-lived intangible asset. Excludes goodwill and capitalized cost for software to be sold, leased, or marketed.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase in finite-lived intangible asset acquired in business combination, asset acquisition, and from joint venture formation. Excludes goodwill and capitalized cost for software to be sold, leased, or marketed.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 805
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478072/944-805-50-1

+ Details

Name:	us-gaap_FinitelivedIntangibleAssetsAcquired1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration