Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 64,208	$ 69,444
Accretion of discount		2,343	2,393
Liability incurred		4,373	2,632
Liability settled		(3,261)	(4,493)
Liability sold		(2,953)	(281)
Revision of estimates	[1]	1,917	(5,487)
ARO liability, December 31:		66,627	64,208
Less current portion		2,920	1,437
Total long-term ARO liability		$ 63,707	$ 62,771

[1] Plugging liability estimates were revised in both 2019 and 2018 for updates in the cost of services used to plug wells over the preceding year. We had various upward and downward adjustments and changes in estimated timing of cash flows.