Derivative Instruments - Effect of Derivative Contracts on Condensed Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Foreign Exchange Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized from derivative contracts in the condensed consolidated statement of income	$ 15	$ (30)
Foreign Exchange Contract | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized from derivative contracts in the condensed consolidated statement of income	20	(28)
Foreign Exchange Contract | Revenues | Designated as Hedging Instrument | Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized from derivative contracts in the condensed consolidated statement of income	20	(28)
Foreign Exchange Contract | Interest and Other, Net | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized from derivative contracts in the condensed consolidated statement of income	(5)	(2)
Interest Rate Contract | Interest and Other, Net | Designated as Hedging Instrument | Fair Value Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) from interest rate contracts designated as fair value hedges recognized in interest and other, net	15	(30)
Gain (loss) from hedged items attributable to hedged risk recognized in interest and other, net	(15)	30
Gain (loss) recognized from derivative contracts in the condensed consolidated statement of income	0	0
Warrant | Interest and Other, Net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) from hedged items attributable to hedged risk recognized in interest and other, net	$ 113	$ 0