Accumulated Other Comprehensive Income (Schedule Of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 30, 2017	[1]	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and interest expense										$ 2,598	$ 2,457	$ 1,552
Provision for income taxes										19,391	(37,499)	(33,001)
Net income	$ 63,654		$ 4,449	$ 18,475	$ 11,836	$ 41,140	$ 10,628	$ 15,265	$ 20,129	98,414	87,162	59,330
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and interest expense										(40)	437	27
Provision for income taxes										11	(180)	(11)
Net income										$ (29)	$ 257	$ 16

[1] The quarter ended December 30, 2017 includes the tax benefit of $49.3 million as a result of revaluing the Company's net deferred tax liability using the enacted Federal tax rate of 21% under the Tax Reform.