Goodwill and Acquired Intangible Assets - Aggregate Amortization Expense for Acquired Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 5	$ 11	$ 40
Amortization expense - Remainder of 2016	10
Amortization expense - 2017	7
Amortization expense - 2018	3
Amortization expense - 2019	$ 2