Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Oct. 04, 2015	Jun. 28, 2015	Dec. 28, 2014	Sep. 28, 2014	Jun. 29, 2014	Dec. 29, 2013	Oct. 25, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High	$ 2,400
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	$ 519	$ 475	$ 91	$ 1,286	$ 3,430	$ 4,926
Business Combination, Contingent Consideration Arrangements, Description	Contingent consideration is measured at fair value at the acquisition date, based on the probability that revenue thresholds or product development milestones will be achieved during the earnout period, with changes in the fair value after the acquisition date affecting earnings to the extent it is to be settled in cash.
Business Combination, Contingent Consideration Arrangements, Maximum Period	3 years
Business Combination, Contingent Consideration Arrangements, Weighted Average Period	1 year
Line of Credit, Maturing January 8, 2019 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 700,000
Revolving credit facility outstanding balance	492,000		516,000
2021 Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes, face value	500,000						$ 500,000
Long-term Debt, Gross	497,900		497,700
Debt Instrument, Unamortized Discount	2,100		2,300				$ 3,100
Unsecured senior notes, fair value	528,100		542,700
Financing Lease Obligations [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unsecured senior notes, fair value	$ 38,500		$ 39,300