Financial Instruments Measured at Fair Value - Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 27, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		$ 99,000
Available-for-sale securities	$ 42,814	38,109
Interest rate swaps	569	378
Foreign exchange contracts	867	694
Contingent consideration	(3,528)	(6,202)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	40,722	131,979
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		99,000
Available-for-sale securities	42,814	38,109
Interest rate swaps	0	0
Foreign exchange contracts	0	0
Contingent consideration	0	0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	42,814	137,109
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Available-for-sale securities	0	0
Interest rate swaps	569	378
Foreign exchange contracts	867	694
Contingent consideration	0	0
Total Fair Value Assets And Liabilities Measured On Recurring Basis	1,436	1,072
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Available-for-sale securities	0	0
Interest rate swaps	0	0
Foreign exchange contracts	0	0
Contingent consideration	(3,528)	(6,202)
Total Fair Value Assets And Liabilities Measured On Recurring Basis	$ (3,528)	$ (6,202)