Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 98,297	$ 100,567
Accretion of discount		2,779	3,453
Liability incurred		584	6,754
Liability settled		(1,215)	(2,893)
Liability sold		(10,882)	(421)
Revision of estimates	[1]	(19,393)	(9,163)
ARO liability, December 31:		70,170	98,297
Less current portion		2,906	3,965
Total long-term ARO liability		$ 67,264	$ 94,332

[1] Plugging liability estimates were revised in both 2016 and 2015 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.