Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Income Statement [Abstract]
Net sales	$ 531,155	$ 474,778	$ 1,288,659	$ 1,257,186
Cost of sales	196,195	178,388	488,558	481,377
Gross profit	334,960	296,390	800,101	775,809
Operating expenses:
Sales and marketing	211,574	213,133	549,483	568,799
General and administrative	44,127	35,098	111,915	102,466
Research and development	9,644	9,007	28,399	25,440
Total operating expenses	265,345	257,238	689,797	696,705
Operating income	69,615	39,152	110,304	79,104
Interest expense, net	1,827	3,131	8,111	8,968
Income before income taxes	67,788	36,021	102,193	70,136
Income tax expense	16,468	7,967	24,363	12,384
Net income	$ 51,320	$ 28,054	$ 77,830	$ 57,752
Basic net income per share:
Net income per share – basic (in dollars per share)	$ 1.83	$ 0.96	$ 2.79	$ 1.93
Weighted-average shares – basic (in shares)	27,973,000	29,085,000	27,918,000	29,859,000
Diluted net income per share:
Net income per share – diluted (in dollars per share)	$ 1.79	$ 0.94	$ 2.73	$ 1.88
Weighted-average shares – diluted (in shares)	28,634,000	29,796,000	28,560,000	30,688,000