Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 66,627	$ 64,208
Accretion of discount		(596)	(562)
Liability incurred		314	3,116
Liability settled		(319)	(1,636)
Liability sold		(15)	(549)
Revision of estimates	[1]	(3,384)	2,139
ARO liability, March 31:		63,819	67,840
Less: current portion		1,470	1,742
Total long-term ARO		$ 62,349	$ 66,098

[1] Plugging liability estimates were revised in both 2020 and 2019 for updates in the cost of services used to plug wells over the preceding year. We had various upward and downward adjustments.