Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization of Intangible Assets	$ 2	$ 2	$ 6	$ 6