Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Feb. 01, 2018	Dec. 31, 2016
Subsequent Event [Line Items]
Net proceeds from public offering		$ 64,613
Subsequent Event | American Depositary Shares
Subsequent Event [Line Items]
Issuance of stock (shares)	19,178,082
Over allotment option, exercisable period	30 days
Sale of stock price per share	$ 3.41
Net proceeds from public offering	$ 65,000
Subsequent Event | American Depositary Shares | Over-Allotment Option
Subsequent Event [Line Items]
Issuance of stock (shares)	2,876,712