Restructuring of Operations - Additional Information (Details) $ in Millions		3 Months Ended			6 Months Ended
	Jun. 30, 2015 employee	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring expense		$ 11		$ 3	$ 12	$ 12
Estimated reduction of employees | employee	250
Restructuring and related activities, completion date period	2 years
Employee Termination Benefits [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense		$ 11				8
Exit Costs [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expense			$ 1			$ 4