Preferred Stock - Change in Redemption Value of Convertible Preferred Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Temporary Equity [Line Items]
Adjustment to redemption value	$ 374,015	$ 49,849	$ 5,713
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	46,976	6,447
Series B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	36,961	2,836	28
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	52,832	2,449	5,685
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	237,246	38,117
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	$ 374,015	$ 49,849	$ 5,713