Borrowings - Long-Term Debt, Debt Issued (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Euro fixed-rate notes
Notes Issued
Aggregate amount of debt issued		$ 4,100
Fixed rate debt due in 2021
Notes Issued
Outstanding debt redeemed		$ 2,900
Aggregate principal redeemed (as a percent)		100.00%
Loss upon redemption on notes		$ (49)
IBM Credit LLC \| Fixed rate debt due in 2021 to 2023
Notes Issued
Outstanding debt redeemed	$ 1,750
Aggregate principal redeemed (as a percent)	100.00%
Loss upon redemption on notes	$ (22)

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=117329964&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Section 40
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

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Balance Type:	credit
Period Type:	duration