Accumulated Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Parentheticals) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Unrealized loss on interest rate swaps, net of tax of $137	$ (22)	$ 9	$ (137)	$ (1,006)
Reclassification of loss into earnings from interest rate swaps, net of tax of $369	110	117	369	339
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net of tax of $9	(3)	(4)	(9)	(12)
Reclassification of prior service credits into earnings from postretirement benefit plans, net of tax of $1	$ 0	$ 0	(1)	$ (1)
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 $137			(137)
Reclassification of loss into earnings from interest rate swaps, net of tax of $369			369
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 $9			(9)
Reclassification of prior service credits into earnings from postretirement benefit plans, net of tax of $1			$ (1)