Revenue Recognition (Schedule Of Breakout Of The Company's Derived Revenue And Other Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue Recognition [Abstract]
Revenue from contracts with customers	$ 36,103	$ 52,445	$ 123,760	$ 98,057
Interest income	5	5	6	9
Cost recovery income	158	417	158	417
Dividend income		18		18
Total revenue	$ 36,266	$ 52,885	$ 123,924	$ 98,501