Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Apr. 05, 2017	Aug. 04, 2015	Jul. 29, 2015	Dec. 31, 2017	Dec. 31, 2015	Mar. 30, 2017	Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized				100,000,000			100,000,000
Common stock, par value				$ 0.001			$ 0.001
Preferred stock, shares authorized				5,000,000			5,000,000
Preferred stock, par value				$ 0.001			$ 0.001
Common stock, shares outstanding				32,662,255			27,296,863
Preferred stock, shares issued				0			0
Preferred stock, shares outstanding				0			0
Follow-on Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Public offering price per share				$ 18.00	$ 18.60
Common Stock [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares subscribed						5,117,500
Common Stock [Member] | Follow-on Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued			3,763,440	5,117,500	4,327,956
Public offering price per share		$ 18.60				$ 18.00
Proceeds from issuance of common stock net of underwriting discounts and offering costs	$ 86,224	$ 75,231
Offering expenses paid	$ 5,891	$ 5,269
Common Stock [Member] | Underwriter's Over-Allotment [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	667,500	564,516
Common stock, shares subscribed						667,500