Financial Instruments Measured at Fair Value - Unobservable Inputs Reconciliation (Details) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Measurements, Recurring [Member] - Contingent Consideration [Member] $ in Thousands	9 Months Ended
	Sep. 26, 2015 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of December 31, 2014	$ (6,202)
Fair value of initial contingent consideration	0
Change in fair value of contingent consideration included in earnings	(853)
Payment of contingent consideration	3,000	[1]
Foreign currency translation adjustment	351
Balance as of September 26, 2015	$ (3,704)

[1] Contingent consideration payment relates to an acquisition completed prior to 2015.