Significant Accounting Policies - Revenue Recognition for Major Categories of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Amount of revenue deferred and recognized over the shipping period	$ 0
Period of PCS support	1 year
Services
Disaggregation of Revenue [Line Items]
Deferred income	$ 4,994	$ 5,106
Contract assets	448	424
Unbilled services accounts receivable included in notes and accounts receivable - trade	$ 1,008	$ 1,071
Services \| Minimum
Disaggregation of Revenue [Line Items]
Contract term, high end of range	10 years
Services \| Maximum
Disaggregation of Revenue [Line Items]
Contract term, low end of range	1 year
Term License Software
Disaggregation of Revenue [Line Items]
Committed contract term	1 month
Open Source Software
Disaggregation of Revenue [Line Items]
Standalone selling price	$ 0
Allocation of consideration to open source software license	0
Revenue recognized when control is transferred to client	$ 0

The period of time over which a contract with customer extends.

No definition available.

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- Definition

The high end of the range of the period of time over which a contract with customer extends.

+ References

No definition available.

+ Details

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- Definition

The low end of the range of the period of time over which a contract with customer extends.

+ References

No definition available.

+ Details

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- Definition

The duration of PCS sold as a packaged bundle with perpetual software licenses where the standalone selling price may be determined using the residual approach.

+ References

No definition available.

+ Details

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- Definition

Amount of revenue deferred and recognized during the shipping period.

+ References

No definition available.

+ Details

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- Definition

Amount of consideration for open source software that is allocated to the license when it is a distinct performance obligation.

+ References

No definition available.

+ Details

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- Definition

Amount of open source software revenue recognized at transfer of control.

+ References

No definition available.

+ Details

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- Definition

The standalone selling price of open source software under an open source licensing model.

+ References

No definition available.

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- Definition

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
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- Definition

Amount of obligation to transfer good or 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
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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

Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 912
-SubTopic 310
-Section 45
-Paragraph 2
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