Summary Of Significant Accounting Policies (Effect Of The Adoption Of ASC 2014-09 On Financial Statements) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes	$ 25,285	$ 24,585	$ 24,746
Deferred current revenue	6,796	9,495	9,850
Retained earnings	$ 42,655	$ 33,250	33,056
Adjustments [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes			(162)
Retained earnings			377
Adjustments [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes			(161)
Deferred current revenue			(355)
Retained earnings			$ 194