Financial Instruments Measured at Fair Value - AFS (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 28, 2014	Dec. 31, 2013
Marubun [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Investment Ownership Percentage	8.40%
Cost basis	$ 10,016	$ 10,016
Unrealized holding gain	4,311	2,709
Fair value	14,327	12,725
WPG [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Investment Ownership Percentage	1.90%
Cost basis	10,798	10,798
Unrealized holding gain	31,710	24,903
Fair value	42,508	35,701
Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost basis	15,735	15,614
Unrealized holding gain	6,732	5,817
Fair value	$ 22,467	$ 21,431