Common Stock Issuance - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Feb. 28, 2017	Sep. 30, 2017	Sep. 30, 2016
Proceeds from Issuance or Sale of Equity [Abstract]
Number of common stock issued	834,896
Weighted average sale price for common stock issuance	$ 23.96
Gross proceeds from common stock issuance	$ 20,000
Net proceeds from common stock issuance	$ 19,300	$ 19,294	$ 0