Commitments - Extended Warranty Liability (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Movement in deferred income
Amortization of deferred revenue	$ (4,500)			$ (6,500)
Current portion	12,469	$ 12,469		12,026
Noncurrent portion	3,787	3,787		3,851
Extended Warranty
Movement in deferred income
Beginning Balance		477	$ 533	533
Revenue deferred for new extended warranty contracts		93	81
Amortization of deferred revenue		(115)	(128)
Other		(9)	0
Ending Balance	445	445	486	$ 477
Current portion	216	216	225
Noncurrent portion	$ 228	$ 228	$ 260

Increase in contract with customer liability for new contracts.

No definition available.

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- Definition

Increase (decrease) in contract with customer liability for other changes not specified in the taxonomy, including foreign currency translation adjustments.

+ References

No definition available.

+ Details

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Namespace Prefix:	ibm_
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- References

No definition available.

+ Details

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- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(5))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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- Definition

Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as current.

+ References

+ Details

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- Definition

Amount of deferred income and obligation to transfer product and service to customer for which consideration has been received or is receivable, classified as noncurrent.

+ References

+ Details

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Balance Type:	credit
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- Details

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Namespace Prefix:
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Period Type: