Company and Nature of Business - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	6 Months Ended
	Jun. 14, 2017	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Subsidiary Or Equity Method Investee [Line Items]
Accumulated deficit		$ 274,719	$ 274,719	$ 195,106
Common stock, shares issued		58,736,529	58,736,529	42,342,706
Convertible Bonds
Subsidiary Or Equity Method Investee [Line Items]
Convertible bonds, aggregate principal value	$ 68,000
Convertible bonds, carrying value	$ 55,800
Common Stock
Subsidiary Or Equity Method Investee [Line Items]
Aggregate cash proceeds net of underwriting discounts and commissions and offering costs		$ 64,200
Underwriting discounts and commissions		6,100	$ 6,100
Offering costs		$ 5,600	$ 5,600
Common Stock | Convertible Bonds
Subsidiary Or Equity Method Investee [Line Items]
Shares issued upon conversion	7,727,273
IPO
Subsidiary Or Equity Method Investee [Line Items]
Common stock, shares issued		6,900,000	6,900,000
Common stock share price		$ 11.00	$ 11.00
IPO | Common Stock
Subsidiary Or Equity Method Investee [Line Items]
Common stock share price		$ 11.00	$ 11.00
IPO | Common Stock | Convertible Bonds
Subsidiary Or Equity Method Investee [Line Items]
Shares issued upon conversion			7,727,273