Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 64,208	$ 69,444
Accretion of discount		1,770	1,829
Liability incurred		4,325	244
Liability settled		(2,805)	(3,907)
Liability sold		(1,721)	(105)
Revision of estimates	[1]	(1,705)	(4,778)
ARO liability, September 30:		64,072	62,727
Less current portion		3,033	1,451
Total long-term ARO		$ 61,039	$ 61,276

[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.