Marketable Securities (Schedule Of Marketable Securities Classified As Cash Equivalents) (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Gain (Loss) on Investments [Line Items]
Cost	$ 2,300,000	$ 1,600,000
Foreign Accounts
Gain (Loss) on Investments [Line Items]
Cash And Marketable Securities Held In Foreign Accounts	$ 532,000	$ 187,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ScheduleOfGainLossOnInvestmentsIncludingMarketableSecuritiesAndInvestmentsHeldAtCostIncomeStatementReportedAmountsSummaryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration