Segment Information and Operations By Geographic Area (Schedule Of Reportable Segment And Reconciliation Of Segment Contribution Income To Income Before Income Taxes) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 03, 2016	Jun. 28, 2015	Jul. 03, 2016	Jun. 28, 2015
Segment Reporting Information [Line Items]
Total net revenues		$ 311,655	$ 288,782	$ 621,911	$ 597,939
Total segment contribution income		52,463	32,706	106,057	74,026
Corporate and unallocated costs		(16,418)	(12,230)	(33,134)	(25,196)
Amortization of intangible assets	[1]	(4,166)	(4,243)	(8,331)	(8,639)
Stock-based compensation expense		(5,019)	(4,058)	(9,430)	(8,406)
Restructuring and other charges		(1,311)	(974)	(3,989)	(5,368)
Losses on inventory commitments due to restructuring		0	0	0	(407)
Litigation reserves, net		(35)	0	(45)	2,690
Interest income		279	67	513	119
Other income (expense), net		(332)	(343)	(698)	132
Income before income taxes		25,461	10,925	50,943	28,951
Retail [Member]
Segment Reporting Information [Line Items]
Total net revenues		170,646	131,809	328,189	252,766
Total segment contribution income		$ 25,660	$ 16,247	$ 49,959	$ 32,566
Segment contribution margin (in percentage)		15.00%	12.30%	15.20%	12.90%
Commercial [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 73,671	$ 63,017	$ 142,103	$ 135,748
Total segment contribution income		$ 18,551	$ 12,564	$ 33,388	$ 28,807
Segment contribution margin (in percentage)		25.20%	19.90%	23.50%	21.20%
Service Provider [Member]
Segment Reporting Information [Line Items]
Total net revenues		$ 67,338	$ 93,956	$ 151,619	$ 209,425
Total segment contribution income		$ 8,252	$ 3,895	$ 22,710	$ 12,653
Segment contribution margin (in percentage)		12.30%	4.10%	15.00%	6.00%

[1] Amount excludes amortization expense related to patents included in cost of revenue.