Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015	Aug. 31, 2014
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized	0	126,374,911
Convertible preferred stock, shares issued and outstanding		77,185,117
Convertible preferred stock, carrying value		$ 36,996
Convertible preferred stock, aggregate liquidation preference		$ 41,538
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 1.0000
Convertible preferred stock, shares authorized		6,037,500
Convertible preferred stock, shares issued and outstanding		6,037,500
Convertible preferred stock, carrying value		$ 1,751
Convertible preferred stock, aggregate liquidation preference		$ 6,038
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 0.5000		$ 0.50
Convertible preferred stock, shares authorized		40,000,000
Convertible preferred stock, shares issued and outstanding		36,000,000
Convertible preferred stock, carrying value		$ 18,825
Convertible preferred stock, aggregate liquidation preference		$ 18,000
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 0.4979	$ 0.4979
Convertible preferred stock, shares authorized		80,337,411	80,337,411
Convertible preferred stock, shares issued and outstanding		35,147,617
Convertible preferred stock, carrying value		$ 16,420
Convertible preferred stock, aggregate liquidation preference		$ 17,500