Derivative Instruments - Notional Amount of Derivatives Outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Notional amount	$ 5,032	$ 4,242	$ 2,588
Foreign Exchange Contract | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	1,317	1,535	2,257
Cash Flow Hedging | Foreign Exchange Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	1,315	307	331
Fair Value Hedging | Interest Rate Contract | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount	$ 2,400	$ 2,400	$ 0