Goodwill and Acquired Intangible Assets - Aggregate Amortization Expense for Acquired Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 2	$ 11	$ 7	$ 22	$ 40
Amortization expense - Remainder of 2016	10		10
Amortization expense - 2017	7		7
Amortization expense - 2018	3		3
Amortization expense - 2019	$ 2		$ 2