Derivative Instruments (Forward Currency Exchange Contracts) (Details) - Foreign currency exchange forward contracts - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional amount	$ 3,899	$ 4,950
Maximum term	548 days	546 days
Derivative, fair value, net	$ 27	$ 59
Other current assets
Derivative [Line Items]
Derivative asset	41	68
Other noncurrent assets
Derivative [Line Items]
Derivative asset	4	1
Other current liabilities
Derivative [Line Items]
Derivative liability	(16)	(9)
Other noncurrent liabilities
Derivative [Line Items]
Derivative liability	(2)	(1)
Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	1,058	889
Derivative, fair value, net	17	21
Designated as Hedging Instrument | Other current assets
Derivative [Line Items]
Derivative asset	24	27
Designated as Hedging Instrument | Other noncurrent assets
Derivative [Line Items]
Derivative asset	4	1
Designated as Hedging Instrument | Other current liabilities
Derivative [Line Items]
Derivative liability	(9)	(6)
Designated as Hedging Instrument | Other noncurrent liabilities
Derivative [Line Items]
Derivative liability	(2)	(1)
Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	2,841	4,061
Derivative, fair value, net	10	38
Not Designated as Hedging Instrument | Other current assets
Derivative [Line Items]
Derivative asset	17	41
Not Designated as Hedging Instrument | Other noncurrent assets
Derivative [Line Items]
Derivative asset	0	0
Not Designated as Hedging Instrument | Other current liabilities
Derivative [Line Items]
Derivative liability	(7)	(3)
Not Designated as Hedging Instrument | Other noncurrent liabilities
Derivative [Line Items]
Derivative liability	$ 0	$ 0