Fair Value of Financial Instruments (Details 5) (Assets and liabilities measured at fair value on recurring basis, Contingent consideration, USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 28, 2014	Jun. 28, 2014
Assets and liabilities measured at fair value on recurring basis | Contingent consideration
Fair value liabilities reconciliation of changes
Balance at the beginning of the period	$ 13,256	$ 12,919
Gain recognized in earnings	(1,301)	(964)
Balance at the end of the period	11,955	11,955
Net gain for the period included in earnings attributable to contingent consideration held at the end of the period:	$ 1,301	$ 964