Stock Compensation - Summary of Option Activity in 2015 Plan, 2007 Plan and 1999 Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding at beginning of year	223,432
Shares, Exercised	(64,200)
Shares, Outstanding at end of period	159,232
Shares, Shares subject to options exercisable at end of period	159,232
Weighted average exercise price, Outstanding at beginning of year	$ 3.93
Weighted average exercise price, Exercised	2.04
Weighted average exercise price, Outstanding at end of period	4.70
Weighted average exercise price, Shares subject to options exercisable at end of period	$ 4.70
Aggregate intrinsic value, Outstanding at end of period	$ 986
Aggregate intrinsic value, Shares subject to options exercisable at end of period	$ 986