Accumulated Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Parentheticals) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gain (loss) on interest rate swaps, net of tax of $937	$ (731)	$ (9)	$ (937)	$ (761)
Reclassification of loss into earnings from interest rate swaps, net of tax of $172	71	32	172	99
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net of tax of $12	(4)	(4)	(12)	(12)
Reclassification of prior service credits into earnings from postretirement benefit plans, net of tax of $28	$ (9)	$ (8)	(28)	$ (25)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized gain (loss) on interest rate swaps, net of tax of $937			(937)
Reclassification of loss into earnings from interest rate swaps, net of tax of $172			172
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net of tax of $12			(12)
Reclassification of prior service credits into earnings from postretirement benefit plans, net of tax of $28			$ (28)