Accumulated Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Parentheticals) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized loss on interest rate swaps, net of tax of $1,006	$ 9	$ (731)	$ (1,006)	$ (937)
Reclassification of loss into earnings from interest rate swaps, net of tax of $339	117	71	339	172
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 $1	$ 0	$ (9)	(1)	$ (28)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized loss on interest rate swaps, net of tax of $1,006			(1,006)
Reclassification of loss into earnings from interest rate swaps, net of tax of $339			339
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 $1			$ (1)