Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 27, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 28, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Dec. 27, 2014	Dec. 28, 2013	Dec. 29, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income									$ 2,287	$ 4,684	$ 3,468
Provision for income taxes									(29,831)	(44,145)	(48,403)
Net income	13,896	13,707	12,798	14,766	15,721	11,692	24,179	20,129	55,167	71,721	82,511
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									63	1,774	713
Provision for income taxes									(26)	(730)	(293)
Net income									$ 37	$ 1,044	$ 420