Marketable Securities (Schedule Of Marketable Securities Classified As Cash Equivalents) (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Cost	$ 3,164,000	$ 5,195,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Recorded Basis	3,164,000	5,195,000
Money Market And Certificates Of Deposit
Gain (Loss) on Investments [Line Items]
Cost	3,164,000	5,195,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Recorded Basis	3,164,000	5,195,000
Foreign Accounts
Gain (Loss) on Investments [Line Items]
Cash And Marketable Securities Held In Foreign Accounts	$ 197,000	$ 614,000