Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Apr. 01, 2017
Income Statement [Abstract]
Net sales	$ 388,633	$ 393,899
Cost of sales	151,156	147,440
Gross profit	237,477	246,459
Operating expenses:
Sales and marketing	171,917	169,266
General and administrative	31,734	33,769
Research and development	6,925	7,596
Total operating expenses	210,576	210,631
Operating income	26,901	35,828
Other expense, net	(525)	(138)
Income before income taxes	26,376	35,690
Income tax expense	5,828	11,229
Net income	$ 20,548	$ 24,461
Basic net income per share:
Net income per share – basic	$ 0.54	$ 0.57
Weighted-average shares – basic	38,244,000	42,750,000
Diluted net income per share:
Net income per share – diluted	$ 0.52	$ 0.56
Weighted-average shares – diluted	39,347,000	43,712,000