Quarterly Financial Data - Condensed Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 116,896	$ 105,247	$ 108,942	$ 102,738	$ 108,537	$ 98,497	$ 104,075	$ 98,679	$ 433,823	$ 409,788	$ 396,489
Cost of sales	23,562	23,717	23,177	22,581	23,320	19,880	22,516	22,137	93,037	87,853	86,525
Gross profit	93,334	81,530	85,765	80,157	85,217	78,617	81,559	76,542	340,786	321,935	309,964
Operating expense	75,474	72,496	77,767	74,238	77,801	69,346	84,254	69,467	299,975	300,868
Operating income	17,860	9,034	7,998	5,919	7,416	9,271	(2,695)	7,075	40,811	21,067	9,255
Net income (loss) from continuing operations	1,516	3,348	4,735	(2,308)	(5,117)	10,384	(6,346)	4,576	7,291	3,497	(2,342)
Net income (loss)	$ 1,568	$ 3,456	$ 3,853	$ (2,654)	$ (3,236)	$ 9,896	$ (7,444)	$ 3,840	$ 6,223	$ 3,056	$ (2,809)
Net income (loss) per common share—basic
Net income (loss) from continuing operations	$ 0.08	$ 0.18	$ 0.26	$ (0.13)	$ (0.29)	$ 0.57	$ (0.35)	$ 0.25	$ 0.40	$ 0.19	$ (0.12)
Net income (loss)	0.09	0.19	0.21	(0.15)	(0.18)	0.55	(0.41)	0.21	0.34	0.17	(0.15)
Net income (loss) per common share—diluted
Net income (loss) from continuing operations	0.08	0.18	0.26	(0.13)	(0.29)	0.56	(0.35)	0.24	0.39	0.19	(0.12)
Net income (loss)	$ 0.08	$ 0.19	$ 0.21	$ (0.15)	$ (0.18)	$ 0.54	$ (0.41)	$ 0.20	$ 0.34	$ 0.17	$ (0.15)