Selected Quarterly Financial Data (unaudited) (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
Quarterly Financial Information Disclosure [Abstract]
Total out of period adjustments									$ 1,800
Net sales	$ 114,791	$ 104,836	$ 99,226	$ 101,215	$ 94,651	$ 90,262	$ 79,643	$ 79,242	420,068	$ 343,798	$ 268,245
Gross margin	65,346	65,633	63,143	64,461	63,016	49,765	45,637	48,670	258,583	207,088	170,536
Net income	$ 2,083	$ 5,711	$ 8,485	$ 12,926	$ (2,071)	$ 422	$ 2,276	$ 4,580	$ 29,205	$ 5,207	$ 17,297
Earnings per share
Basic (in dollars per share)	$ 0.04	$ 0.10	$ 0.15	$ 0.24	$ (0.04)	$ 0.01	$ 0.04	$ 0.09	$ 0.52	$ 0.10	$ 0.33
Diluted (in dollars per share)	$ 0.03	$ 0.10	$ 0.15	$ 0.24	$ (0.04)	$ 0.01	$ 0.04	$ 0.09	$ 0.50	$ 0.10	$ 0.32
Decrease to net sales									$ 900
Increase sales, general and administration expense									$ 1,300
Decrease to provision income taxes	$ 400