General (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 28, 2017	Sep. 27, 2018	Sep. 28, 2017	Sep. 27, 2018		Sep. 28, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning Balance, Interest Rate Swaps	$ 0			$ 0
Other comprehensive income before reclassifications, Interest Rate Swaps		$ 192	$ 0	191		$ 0
Amounts reclassified from accumulated other comprehensive loss, Interest Rate Swaps	0	46	0	134	[1]	0
Net other comprehensive income (loss), Interest Rate Swaps				325
Ending Balance, Interest Rate Swaps	0	325		325
Beginning Balance, Available for Sale Investments	(11)			0		3
Change in unrealized gain on available for sale investments, Available for Sale Investments		0	0	0		(14)
Other comprehensive income before reclassifications, Available for Sale Investments				0
Amount reclassified to retained earnings on December 29, 2017 in connection with the adoption of ASU No. 2016-01	11			0
Net other comprehensive income (loss), Available for Sale InvestmentsNet other comprehensive income (loss), Available for Sale Investments				0		(14)
Ending Balance, Available for Sale Investments	0	0	(11)	0		(11)
Beginning Balance, Pension Obligation	(7,414)			(7,414)		(5,069)
Amortization of net actuarial loss and prior service credit, Pension Obligation		113	54	340		161
Other comprehensive income before reclassifications, Pension Obligation				0
Amounts reclassified from accumulated other comprehensive loss, Pension Obligation	0			0
Net other comprehensive income (loss), Pension Obligation				340		161
Ending Balance, Pension Obligation	(7,414)	(7,074)	(4,908)	(7,074)		(4,908)
Beginning Balance, Accumulated Other Comprehensive Loss	(7,425)			(7,425)		(5,066)
Change in unrealized gain on available for sale investments, Accumulated Other Comprehensive Loss						(14)
Amortization of net actuarial loss and prior service credit, Accumulated Other Comprehensive Loss		113	54	340		161
Other comprehensive income before reclassifications, Accumulated Other Comprehensive Loss				191
Amounts reclassified from accumulated other comprehensive loss, Accumulated Other Comprehensive Loss	11			134	[1]
Other comprehensive income		351	54	665		147
Ending Balance, Accumulated Other Comprehensive Loss	$ (7,425)	$ (6,749)	$ (4,919)	$ (6,749)		$ (4,919)

[1] Amount is included in interest expense in the consolidated statements of earnings.