Derivatives and Hedging - Notional and fair values of derivative instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Other Current Assets [Member]
Derivative [Line Items]
Derivative Assets	$ 15	$ 24
Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative Assets	17	22
Other Current Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities	13	52
Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities	5	6
Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional Amount	778	1,200
Derivative Assets	32	46
Derivative Liabilities	18	58
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount	1,058	1,365
Derivative Assets	32	46
Derivative Liabilities	18	58
Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional Amount	280	165
Derivative Assets	0	0
Derivative Liabilities	$ 0	$ 0
Term of contract ( in days)	30 days