Valuation And Qualifying Accounts (Schedule Of Valuation And Qualifying Accounts) (Details) - Allowance For Doubtful Accounts [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		$ 2,270	$ 2,865	$ 3,298
Additions (Reductions) Charged to Costs and Expenses		1,777	(262)	(120)
Additions (Reductions) Charged to Other Accounts		(198)	(95)	223
Deductions	[1]	(763)	(238)	(536)
Balance at End of Period		$ 3,086	$ 2,270	$ 2,865

[1] Uncollectible accounts written off, net of recoveries.