Accumulated Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jul. 01, 2017	Jun. 30, 2018	Jul. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) - total			$ (1,299)
Unrealized gain on interest rate swaps, net	$ 323	$ (223)	1,128	$ (188)
Reclassification of loss into earnings from interest rate swaps, net	177	201	406	423
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net	(7)	(5)	(15)	(10)
Reclassification of prior service credits into earnings from postretirement benefit plans, net	(1)	$ (1)	(2)	$ (1)
Accumulated other comprehensive income (loss) - total	218		218
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			(1,587)
Unrealized gain on interest rate swaps, net			1,128
Reclassification of loss into earnings from interest rate swaps, net			406
Accumulated other comprehensive income (loss) - total	(53)		(53)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) - total			288
Reclassification of net actuarial gain into earnings from postretirement benefit plans, net			(15)
Reclassification of prior service credits into earnings from postretirement benefit plans, net			(2)
Accumulated other comprehensive income (loss) - total	$ 271		$ 271