Borrowings - Carrying Value of Convertible Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Principal amount of the Convertible Notes	$ 1,088,941	$ 1,104,598
Unamortized discount	(22,999)	(36,197)
Net carrying amount	1,065,942	1,068,401
Convertible Notes Payable
Debt Instrument [Line Items]
Principal amount of the Convertible Notes	399,600	399,900
Unamortized discount	(23,000)	(36,200)
Net carrying amount	$ 376,600	$ 363,700