Convertible Notes, Net - Summary of Details of Net Book Value of Convertible Note (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Deferred financing costs	$ (17,462)	$ (15,272)
Net book value	562,741	166,762
Convertible Senior Note [Member]
Debt Instrument [Line Items]
Face Value	575,000	172,500
Unamortized discount	(11,386)	(5,532)
Deferred financing costs	(873)	(206)
Net book value	$ 562,741	$ 166,762