Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Income Statement [Abstract]
Net sales	$ 284,938	$ 355,963	$ 757,504	$ 782,408
Cost of sales	121,928	138,777	292,363	302,989
Gross profit	163,010	217,186	465,141	479,419
Operating expenses:
Sales and marketing	130,165	168,839	337,909	355,666
General and administrative	36,716	33,045	67,788	67,368
Research and development	8,254	8,057	18,755	16,433
Total operating expenses	175,135	209,941	424,452	439,467
Operating (loss) income	(12,125)	7,245	40,689	39,952
Interest expense, net	3,940	3,228	6,284	5,837
(Loss) income before income taxes	(16,065)	4,017	34,405	34,115
Income tax (benefit) expense	(3,435)	(263)	7,895	4,417
Net (loss) income	$ (12,630)	$ 4,280	$ 26,510	$ 29,698
Basic net (loss) income per share:
Net (loss) income per share – basic (in dollars per share)	$ (0.45)	$ 0.14	$ 0.95	$ 0.98
Weighted-average shares – basic (in shares)	27,923,000	29,873,000	27,890,000	30,247,000
Diluted net (loss) income per share:
Net (loss) income per share – diluted (in dollars per share)	$ (0.45)	$ 0.14	$ 0.93	$ 0.95
Weighted-average shares – diluted (in shares)	27,923,000	30,531,000	28,523,000	31,134,000