Significant Accounting Policies (Schedule of Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Receivables	$ 260	$ 286	$ 270	$ 266	$ 260	$ 270	$ 284	$ 270
Contract Liability	193	$ 212	231	$ 235	193	231	$ 215	$ 232
Increase/(Decrease) [Member]
Disaggregation of Revenue [Line Items]
Receivables	(26)		(14)		(6)
Contract Liability	$ (19)		$ 16		$ (42)	$ (1)