Summary Of Significant Accounting Policies (Effect Of The Adoption Of ASC 2014-09 On Financial Statements) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes	$ 25,776	$ 24,747	$ 24,908
Deferred current revenue	7,341	9,495	9,850
Retained earnings	$ 40,918	$ 32,873	32,679
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes			24,908
Deferred current revenue			9,850
Retained earnings			32,679
Adjustments Due To ASU 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred income taxes			(161)
Deferred current revenue			(355)
Retained earnings			$ 194