Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Revenue:
Net product sales	$ 283,648	$ 246,638	$ 867,192	$ 756,787
Net sales of services and plans	62,441	54,578	186,297	162,294
Total net revenue	346,089	301,216	1,053,489	919,081
Costs applicable to revenue (exclusive of depreciation and amortization):
Products	115,752	99,096	349,099	299,420
Services and plans	46,606	39,568	135,474	115,033
Total costs applicable to revenue	162,358	138,664	484,573	414,453
Operating expenses:
Selling, general and administrative expenses	151,251	134,457	445,714	395,385
Depreciation and amortization	15,352	13,217	44,404	38,237
Asset impairment	0	0	1,000	52
Litigation settlement	0	0	7,000	0
Other expense, net	568	563	744	1,217
Total operating expenses	167,171	148,237	498,862	434,891
Income from operations	16,560	14,315	70,054	69,737
Interest expense, net	14,851	9,728	40,965	29,377
Debt issuance costs	0	0	2,702	0
Earnings before income taxes	1,709	4,587	26,387	40,360
Income tax provision	163	1,561	9,267	15,893
Net income	$ 1,546	$ 3,026	$ 17,120	$ 24,467
Earnings per share:
Basic (in usd per share)	$ 0.03	$ 0.05	$ 0.30	$ 0.44
Diluted (in usd per share)	$ 0.03	$ 0.05	$ 0.29	$ 0.43
Weighted average shares outstanding:
Basic (shares)	56,414	56,211	56,363	56,176
Diluted (shares)	58,459	57,170	58,281	56,814
Comprehensive income:
Net income	$ 1,546	$ 3,026	$ 17,120	$ 24,467
Change in fair value of hedge instruments	2,255	(663)	2,176	(13,245)
Tax (provision) benefit of change in fair value of hedge instruments	(872)	261	(843)	5,219
Comprehensive income	$ 2,929	$ 2,624	$ 18,453	$ 16,441