Significant Accounting Policies - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents maturity period, maximum		90 days
Income tax expense	$ 248	$ 1,338
ASU 2016-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Income tax expense	$ 248	$ 1,338
Decrease in earnings per share basic		$ 0.01