Revenue Recognition and Accounts Receivable - Summary of Consolidated Statement of Operations As Impact of Adoption (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue Recognition And Accounts Receivable [Line Items]
Net sales	$ 111,547	$ 108,942	$ 220,256	$ 211,680
Cost of sales	22,835	23,177	46,982	45,758
Gross profit	88,712	85,765	173,274	165,922
Sales and marketing	51,529	50,471	101,797	99,003
Operating income	7,024	7,998	14,897	13,917
Income tax expense	(1,088)	(3,924)	(6,461)	(7,848)
Net income from continuing operations	$ 933	$ 4,735	$ 6,162	$ 2,427
Net income from continuing operations per common share—basic	$ 0.05	$ 0.26	$ 0.33	$ 0.13
Net income from continuing operations per common share—diluted	$ 0.05	$ 0.26	$ 0.32	$ 0.13
Topic 606 [Member]
Revenue Recognition And Accounts Receivable [Line Items]
Net sales	$ 111,547		$ 220,256
Cost of sales	22,835		46,982
Gross profit	88,712		173,274
Sales and marketing	51,529		101,797
Other operating expenses	30,159		56,580
Operating income	7,024		14,897
Income tax expense	(1,088)		(6,461)
Net income from continuing operations	$ 933		$ 6,162
Net income from continuing operations per common share—basic	$ 0.05		$ 0.33
Net income from continuing operations per common share—diluted	$ 0.05		$ 0.32
Topic 606 [Member] | Based on Historical Accounting under Topic 605 [Member]
Revenue Recognition And Accounts Receivable [Line Items]
Net sales	$ 113,400		$ 214,762
Cost of sales	23,075		45,191
Gross profit	90,325		169,571
Sales and marketing	51,614		101,975
Other operating expenses	30,159		56,580
Operating income	8,552		11,016
Income tax expense	(1,694)		(5,612)
Net income from continuing operations	$ 1,855		$ 3,130
Net income from continuing operations per common share—basic	$ 0.10		$ 0.17
Net income from continuing operations per common share—diluted	$ 0.10		$ 0.16
Topic 606 [Member] | Impact of Adoption of ASC 606
Revenue Recognition And Accounts Receivable [Line Items]
Net sales	$ (1,853)		$ 5,494
Cost of sales	(240)		1,791
Gross profit	(1,613)		3,703
Sales and marketing	(85)		(178)
Operating income	(1,528)		3,881
Income tax expense	606		(849)
Net income from continuing operations	$ (922)		$ 3,032
Net income from continuing operations per common share—basic	$ (0.05)		$ 0.16
Net income from continuing operations per common share—diluted	$ (0.05)		$ 0.16