Concentration Of Credit Risk (Narrative) (Details) - customer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Number of significant customers	8	8
Accounts Receivable [Member]
Concentration Risk [Line Items]
Number of significant customers		5
Concentration risk percentage of accounts receivable	66.90%	59.30%