Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	$ 656	$ 1,824	$ 1,409	$ 2,802
Provision for income taxes	(7,296)	(15,262)	(15,586)	(27,027)
Net income	12,798	24,179	27,564	44,307
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	5	1,322	46	1,369
Provision for income taxes	(2)	(587)	(20)	(608)
Net income	$ 3	$ 735	$ 26	$ 761