Net Income per Share - Computation of Basic and Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic:
Net income available for common stockholders	$ 4,314	$ 5,042	$ 16,918	$ 12,893
Weighted average shares outstanding	19,503	19,124	19,369	18,589
Basic earnings per share	$ 0.22	$ 0.26	$ 0.87	$ 0.69
Diluted:
Net income available for common stockholders	$ 4,314	$ 5,042	$ 16,918	$ 12,893
Weighted-average shares outstanding	19,503	19,124	19,369	18,589
Common stock equivalents, if dilutive	790	1,023	889	1,381
Shares used in computing diluted earnings per common share	20,293	20,147	20,258	19,970
Diluted earnings per share	$ 0.21	$ 0.25	$ 0.84	$ 0.65
Shares excluded in computing diluted earnings per share as those shares would be anti-dilutive	212		213	1