Net Income Per Common Share - Reconciliation of Numerator and Denominator Used in Calculation of Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income	$ 6,782	$ 4,773	$ 2,207	$ 5,351	$ 4,151	$ 3,290	$ 13,762	$ 12,792
Basic:
Weighted average shares of common stock and vested, undelivered restricted stock units outstanding	27,781,080			27,910,030			27,772,509	27,785,024
Diluted:
Weighted average shares of common stock and vested, undelivered restricted stock units outstanding	27,781,080			27,910,030			27,772,509	27,785,024
Effect of potentially dilutive shares	691,519			460,132			639,416	468,280
Total weighted average shares of common stock and vested, undelivered restricted stock units outstanding and potentially dilutive shares	28,472,599			28,370,162			28,411,925	28,253,304
Net Income Per Share:
Basic net income per share	$ 0.24			$ 0.19			$ 0.50	$ 0.46
Diluted net income per share	$ 0.24			$ 0.19			$ 0.48	$ 0.45