Derivative Instruments - Notional Amounts of Derivatives Outstanding (Details) - USD ($) $ in Millions	Sep. 30, 2015	Sep. 30, 2014
Derivatives, Fair Value [Line Items]
Notional amount	$ 5,995	$ 5,104
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	2,890	2,275
Cash Flow Hedging | Foreign Exchange Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	705	429
Fair Value Hedging | Interest Rate Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	$ 2,400	$ 2,400