Derivatives and Hedging - Notional and fair values of derivative instruments (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value
Notional Amount	$ 956	$ 947
Derivative Assets	31	15
Derivative Liabilities	$ 5	14
Term of derivative contract	30 days
Other Current Assets
Derivatives, Fair Value
Derivative Assets	$ 6	6
Amount not offset against collateral, derivative asset	6	4
Other Noncurrent Assets
Derivatives, Fair Value
Derivative Assets	25	9
Amount not offset against collateral, derivative asset	25	9
Other Current Liabilities
Derivatives, Fair Value
Derivative Liabilities	3	7
Amount not offset against collateral, derivative liabilities	2	5
Other Noncurrent Liabilities
Derivatives, Fair Value
Derivative Liabilities	2	7
Amount not offset against collateral, derivative liabilities	1	7
Derivatives accounted for as hedges | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	711	758
Derivative Assets	31	14
Derivative Liabilities	3	13
Gross Amounts Offset in the Statement of Financial Position	0	(1)
Net Amounts of Assets Presented in the Statement of Financial Position	31	13
Gross Amounts Offset in the Statement of Financial Position	0	(1)
Net Amounts of Liabilities Presented in the Statement of Financial Position	3	12
Not Designated as Hedging Instrument | Foreign exchange contracts
Derivatives, Fair Value
Notional Amount	245	189
Derivative Assets	0	1
Derivative Liabilities	$ 2	$ 1