Derivative Instruments - Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2018
Designated as Hedging Instrument | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$ 1	$ 20
Derivative liability, fair value	8	3
Designated as Hedging Instrument | Fair Value Hedging | Interest Rate Swap | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	0	6
Designated as Hedging Instrument | Fair Value Hedging | Foreign Currency Forward Contracts | Other current assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	1	14
Designated as Hedging Instrument | Fair Value Hedging | Foreign Currency Forward Contracts | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	8	3
Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	7	4
Derivative liability, fair value	6	6
Not Designated as Hedging Instrument | Foreign Currency Forward Contracts | Other current assets
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	7	4
Not Designated as Hedging Instrument | Foreign Currency Forward Contracts | Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 6	$ 6