Derivative Instruments - Notional Amounts of Derivatives Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2016
Derivatives, Fair Value [Line Items]
Notional amount	$ 7,109	$ 6,593
Foreign Exchange Contract | Designated as Hedging Instrument | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Notional amount	1,502	1,200
Foreign Exchange Contract | Designated as Hedging Instrument | Net Investment Hedging
Derivatives, Fair Value [Line Items]
Notional amount	96	0
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	3,111	2,993
Interest Rate Contract | Designated as Hedging Instrument | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Notional amount	$ 2,400	$ 2,400