Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 100,567	$ 133,657
Accretion of discount		2,599	3,538
Liability incurred		6,505	2,889
Liability settled		(1,933)	(3,936)
Liability sold		(249)	(1,206)
Revision of estimates	[1]	(12,881)	(38,263)
ARO liability, September 30:		94,608	96,679
Less current portion		3,481	2,718
Total long-term ARO		$ 91,127	$ 93,961

[1] Plugging liability estimates were revised in both 2015 and 2014 to account for changes in the cost of services used to plug wells over the preceding year. We had various upward and downward adjustments.