Accumulated Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) - total				$ (530)
Unrealized gain on interest rate swaps, net		$ 5	$ (139)	43	$ (1,276)
Reclassification of loss into earnings from interest rate swaps, net		158	365	315	573
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net		(6)	(6)	(12)	(13)
Reclassification of prior service credits into earnings from postretirement benefit plans, net		0	(1)	0	(2)
Accumulated other comprehensive income (loss) - total		(184)		(184)
Interest Rate Swap [Member] | Not Designated as Hedging Instrument | Other Nonoperating Income (Expense)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of unrealized loss into earnings from dedesignated interest rate swaps (2)	[1]	(188)	$ 0	(375)	$ 0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) - total				(740)
Unrealized gain on interest rate swaps, net				43
Reclassification of loss into earnings from interest rate swaps, net				315
Accumulated other comprehensive income (loss) - total		(382)		(382)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) - total				210
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net				(12)
Accumulated other comprehensive income (loss) - total		$ 198		$ 198

[1] The amount of gain (loss) recognized in income on the dedesignated portion of interest rate swaps is included in other income or other expense on the Company's Consolidated Condensed Statements of Operations. The amount of expense recognized on the Company's Consolidated Statements of Operations for the terminated portion of interest rate swaps is included in interest expense.