Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 100,567	$ 133,657
Accretion of discount		3,453	4,599
Liability incurred		6,754	6,246
Liability settled		(2,893)	(4,490)
Liability sold		(421)	(1,206)
Revision of estimates	[1]	(9,163)	(38,239)
ARO liability, December 31:		98,297	100,567
Less current portion		3,965	3,204
Total long-term ARO liability		$ 94,332	$ 97,363

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