Derivatives 2 (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Sep. 30, 2018	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Collateral posted under collateralized security arrangements	$ 0	$ 0
Foreign Currency Contracts
Derivatives
Gross notional value of foreign currency contracts outstanding consisting of purchase and sale contracts	$ 720	$ 456
Tenure of foreign currency contracts outstanding	less than six months	less than three months
Net fair value of foreign currency contracts	$ 10	$ 1
Foreign Currency Contracts \| Other Current Assets
Derivatives
Fair value of foreign currency contracts included in "Other current assets"	18	2
Foreign Currency Contracts \| Accrued Expenses and Other Current Liabilities
Derivatives
Fair value of foreign currency contracts included in "Accrued expenses and other current liabilities"	$ 8	$ 1

Tenure of foreign currency contracts outstanding.

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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

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- Definition

The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624258-113959

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- References

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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

Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

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- Definition

Fair value as of the balance sheet date of all foreign currency derivatives not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

+ References

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