Line Of Credit And Commercial Letters Of Credit (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Percentage over LIBOR	0.50%
Letters of credit	$ 1,197,000	$ 1,803,000
Domestic Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit limit	5,000,000	5,000,000
Line of credit outstanding	$ 0	$ 0