Revenue - Capitalized Contract Costs (Details) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Sales Commission
Capitalized Contract Cost [Line Items]
Capitalized contract cost, net	$ 182	$ 182
Capitalized contract cost, amortization	12	26
Transition and transformation contract costs
Capitalized Contract Cost [Line Items]
Capitalized contract cost, net	591	591
Capitalized contract cost, amortization	$ 73	$ 129

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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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

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

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