Accumulated Other Comprehensive Income (Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and interest expense	$ 824	$ 637
Provision for income taxes	(9,238)	(11,778)
Net income	$ 11,836	20,129
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		269
Provision for income taxes		(111)
Net income		$ 158