Derivatives 2 (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Collateral posted under collateralized security arrangements	$ 0	$ 0
Foreign Currency Contracts
Derivatives, Fair Value [Line Items]
Gross notional value of foreign currency contracts outstanding consisting of purchase and sale contracts	$ 825	$ 336
Tenure of foreign currency contracts outstanding	less than three months	less than three months
Net fair value of foreign currency contracts	$ (4)	$ 1
Foreign Currency Contracts | Other Current Assets
Derivatives, Fair Value [Line Items]
Fair value of foreign currency contracts included in "Other current assets"	8	2
Foreign Currency Contracts | Accrued Expenses and Other Current Liabilities
Derivatives, Fair Value [Line Items]
Fair value of foreign currency contracts included in "Accrued expenses and other current liabilities"	$ 12	$ 1