Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 64,208	$ 69,444
Accretion of discount		1,168	1,248
Liability incurred		3,656	211
Liability settled		(2,316)	(3,142)
Liability sold		(1,632)	(94)
Revision of estimates	[1]	2,349	(4,829)
ARO liability, June 30:		67,433	62,838
Less current portion		1,784	1,451
Total long-term ARO		$ 65,649	$ 61,387

[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.