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. 29, 2013	Jun. 30, 2012	Jun. 29, 2013	Jun. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	$ 1,824	$ 1,162	$ 2,802	$ 2,219
Provision for income taxes	(15,262)	(13,681)	(27,027)	(25,142)
Total amount reclassified, net of tax	24,179	23,204	44,307	43,229
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total amount reclassified, net of tax	735	392	761	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	1,322	705	1,369	708
Provision for income taxes	$ (587)	$ (313)	$ (608)	$ (314)