Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Income Statement [Abstract]
Net sales	$ 263,689	$ 246,817	$ 729,317	$ 714,419
Cost of sales	97,269	86,088	268,083	257,820
Gross profit	166,420	160,729	461,234	456,599
Operating expenses:
Sales and marketing	118,307	101,718	326,477	296,143
General and administrative	15,150	16,936	46,690	50,085
Research and development	2,359	1,742	7,475	4,288
Asset impairment charges	(143)	0	(534)	5,595
Asset impairment charges	48	108	93	115
Total operating expenses	135,721	120,504	380,201	356,226
Operating income	30,699	40,225	81,033	100,373
Other income, net	74	73	243	128
Income before income taxes	30,773	40,298	81,276	100,501
Income tax expense	10,514	14,089	27,620	34,902
Net income	$ 20,259	$ 26,209	$ 53,656	$ 65,599
Basic net income per share:
Net income per share – basic (in USD per share)	$ 0.37	$ 0.47	$ 0.98	$ 1.18
Weighted-average shares – basic (in shares)	54,854	55,444	54,992	55,601
Diluted net income per share:
Net income per share – diluted (in USD per share)	$ 0.36	$ 0.46	$ 0.96	$ 1.15
Weighted-average shares – diluted (in shares)	55,748	56,986	55,990	57,202