Derivative Instruments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Foreign currency cash flow hedge gain to be reclassified during next 12 months	$ 19		$ 19
Foreign currency forward contracts
Derivative [Line Items]
Notional amount of derivatives outstanding	2,300		2,300
Derivatives designated for hedge accounting | Interest rate swap
Derivative [Line Items]
Derivative notional amount	623		623
Derivatives designated for hedge accounting | Cash Flow Hedging | Foreign currency forward contracts
Derivative [Line Items]
Derivative notional amount	467		467
Derivatives not designated for hedge accounting | Foreign currency forward contracts | Other (income) expense, net
Derivative [Line Items]
Pretax (income) expense on derivative instruments	$ 77	$ 3	$ 114	$ 5