Derivative Instruments - Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2017	Mar. 31, 2017
Derivatives designated for hedge accounting | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$ 25	$ 32
Derivative liability, fair value	1	1
Derivatives designated for hedge accounting | Fair Value Hedging | Interest rate swap | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	4	5
Derivatives designated for hedge accounting | Fair Value Hedging | Interest rate swap | Other long-term liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	0	1
Derivatives designated for hedge accounting | Fair Value Hedging | Foreign currency forward contracts | Other current assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	21	27
Derivatives designated for hedge accounting | Fair Value Hedging | Foreign currency forward contracts | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	1	0
Derivatives not designated for hedge accounting
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	21	15
Derivative liability, fair value	12	12
Derivatives not designated for hedge accounting | Foreign currency forward contracts | Other current assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	21	15
Derivatives not designated for hedge accounting | Foreign currency forward contracts | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 12	$ 12