Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2013	Sep. 29, 2012	Sep. 28, 2013	Sep. 29, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	$ 1,129	$ 769	$ 3,931	$ 2,988
Provision for income taxes	(7,281)	(10,053)	(34,308)	(35,195)
Total amount reclassified, net of tax	11,692	17,178	56,000	60,407
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total amount reclassified, net of tax	202		963	394
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	364		1,734	708
Provision for income taxes	$ (162)		$ (771)	$ (314)