Derivatives and Hedging - Notional and fair values of derivative instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value
Notional Amount	$ 996	$ 1,058
Derivative Assets	23	32
Derivative Liabilities	$ 17	18
Term of derivative contract	30 days
Other Current Assets [Member]
Derivatives, Fair Value
Derivative Assets	$ 9	15
Net Amounts of Assets Presented in the Statement of Financial Position	3	6
Other Noncurrent Assets [Member]
Derivatives, Fair Value
Derivative Assets	14	17
Net Amounts of Assets Presented in the Statement of Financial Position	12	13
Other Current Liabilities [Member]
Derivatives, Fair Value
Derivative Liabilities	12	13
Net Amounts of Liabilities Presented in the Statement of Financial Position	7	4
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value
Derivative Liabilities	5	5
Net Amounts of Liabilities Presented in the Statement of Financial Position	3	1
Derivatives accounted for as hedges [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value
Notional Amount	804	778
Derivative Assets	23	32
Derivative Liabilities	17	18
Gross Amounts Offset in the Statement of Financial Position	(8)	(13)
Net Amounts of Assets Presented in the Statement of Financial Position	15	19
Gross Amounts Offset in the Statement of Financial Position	(7)	(13)
Net Amounts of Liabilities Presented in the Statement of Financial Position	10	5
Not Designated as Hedging Instrument [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value
Notional Amount	192	280
Derivative Assets	0	0
Derivative Liabilities	$ 0	$ 0