Derivative Financial Instruments - Derivatives, Other Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
IBM
Derivative Financial Instruments
Liabilities included in master netting arrangements	$ 14	$ 18
Assets included in master netting arrangements	14	18
Fair value hedges \| Interest rate swaps \| IBM
Derivative Financial Instruments
Notional amount	$ 2,550	$ 2,550
Average remaining maturity	1 year 8 months 12 days	2 years
Cash flow hedges \| Interest rate swaps \| IBM
Derivative Financial Instruments
Notional amount	$ 0	$ 0
Net investment hedges \| Foreign exchange contracts \| IBM
Derivative Financial Instruments
Notional amount	$ 1,027	$ 1,229
Average remaining maturity	2 months 12 days	2 months 12 days
Derivative instruments not designated as hedging instruments \| Foreign exchange contracts \| Maximum
Derivative Financial Instruments
Term of derivative contract	1 year
Derivative instruments not designated as hedging instruments \| Foreign exchange contracts \| Third parties
Derivative Financial Instruments
Notional amount	$ 0	$ 0

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 210
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-Section 50
-Paragraph 3
-Subparagraph (d)(1)(i)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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- Definition

Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative liabilities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1A
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-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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