Significant Accounting Policies (Schedule of Contract Assets and Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Receivables	$ 281	$ 260	$ 246	$ 270	$ 281	$ 246	$ 266	$ 270
Contract Liability	236	$ 193	260	$ 231	236	260	$ 235	$ 232
Increase/(Decrease) [Member]
Disaggregation of Revenue [Line Items]
Receivables	21		(24)		15	(24)
Contract Liability	$ 43		$ 29		$ 1	$ 28