Summary Of Significant Accounting Policies (Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 27, 2016	Mar. 29, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit (expense)	$ (6,828)	$ (1,885)
Net loss	(344)	(753)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of pension plan items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial loss	(439)	(750)
Prior service cost	(10)	(6)
Loss before income taxes	(449)	(756)
Income tax benefit (expense)	133	3
Net loss	(316)	(753)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of other postretirement benefit plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Actuarial loss	(28)	0
Loss before income taxes	(28)	0
Income tax benefit (expense)	0	0
Net loss	$ (28)	$ 0