Quarterly Financial Information - Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Selected Quarterly Financial Information [Abstract]
Net sales	$ 105,411	$ 108,413	$ 108,915	$ 98,139	$ 96,892	$ 99,239	$ 97,512	$ 84,569	$ 420,878	$ 378,212	$ 336,634
Gross profit	32,019	33,491	35,203	31,518	30,755	33,535	29,673	24,665	132,231	118,628	109,414
Income before income taxes	7,879	7,856	9,224	7,629	7,691	9,739	6,258	2,118	32,588	25,806	20,953
Net income	$ 5,264	$ 9,054	$ 6,735	$ 5,528	$ 702	$ 6,278	$ 4,156	$ 1,518	$ 26,581	$ 12,654	$ 15,255
Net income, basic	$ 1.05	$ 1.80	$ 1.34	$ 1.10	$ 0.14	$ 1.23	$ 0.81	$ 0.30	$ 5.28	$ 2.48	$ 2.95
Net income, diluted	$ 1.02	$ 1.76	$ 1.33	$ 1.09	$ 0.14	$ 1.23	$ 0.81	$ 0.30	$ 5.21	$ 2.47	$ 2.95