Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2014	Mar. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	$ 753	$ 977
Provision for income taxes	(8,290)	(11,764)
Net income	14,766	20,129
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	41	47
Provision for income taxes	(18)	(21)
Net income	$ 23	$ 26