Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 69,444	$ 70,170
Accretion of discount		2,393	2,886
Liability incurred		2,632	1,948
Liability settled		(4,493)	(2,694)
Liability sold		(281)	(1,735)
Revision of estimates	[1]	(5,487)	(1,131)
ARO liability, December 31:		64,208	69,444
Less current portion		1,437	1,726
Total long-term ARO liability		$ 62,771	$ 67,718

[1] Plugging liability estimates were revised in both 2018 and 2017 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.