Derivative Instruments - Notional Amounts of Derivatives Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2016	Mar. 31, 2015
Derivatives, Fair Value [Line Items]
Notional amount	$ 6,806	$ 5,145
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	2,864	2,256
Cash Flow Hedging | Foreign Exchange Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	1,542	489
Fair Value Hedging | Interest Rate Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	$ 2,400	$ 2,400