Income Taxes (Schedule Of Total Provision For Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current taxes, Federal	$ 0	$ 0	$ (20,612)
Current taxes, State	5	15	(4)
Current taxes	5	15	(20,616)
Deferred taxes, Federal	(62,788)	(62,923)	(535,691)
Deferred taxes, State	5,105	(8,286)	(70,641)
Deferred taxes	(57,683)	(71,209)	(606,332)
Total provision	$ (57,678)	$ (71,194)	$ (626,948)