Pension Plan (Details) - Presentation of the non-service components of periodic pension cost to Pension benefit - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative expenses	$ 1,443	$ 1,414	$ 2,796	$ 2,859
Operating loss	(894)	(1,093)	(755)	(2,189)
Pension benefit	(34)	(8)	(68)	(17)
Loss before income taxes	$ (1,028)	(1,254)	$ (968)	(2,509)
Accounting Standards Update 2017-07 [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative expenses		1,414		2,859
Operating loss		(1,093)		(2,189)
Pension benefit		(8)		(17)
Loss before income taxes		(1,254)		(2,509)
Accounting Standards Update 2017-07 [Member] | Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative expenses		1,406		2,842
Operating loss		(1,085)		(2,172)
Pension benefit
Loss before income taxes		(1,254)		(2,509)
Accounting Standards Update 2017-07 [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
General and administrative expenses		8		17
Operating loss		(8)		(17)
Pension benefit		(8)		(17)
Loss before income taxes