Preferred Stock - Change in Redemption Value of Convertible Preferred Stock (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2015 USD ($)
Temporary Equity [Line Items]
Adjustment to redemption value	$ 11,005
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	5,216
Series B-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	3,513
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	416
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	1,860
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Adjustment to redemption value	$ 11,005