Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Intangible Assets by Major Class
Estimated weighted-average life (in years)			4 years 4 months 24 days
Amortization of Intangible Assets	$ 1	$ 1	$ 2	$ 2