Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 70,170	$ 98,297
Accretion of discount		785	879
Liability incurred		658	90
Liability settled		(630)	(375)
Liability sold	[1]	(432)	(9,950)
Revision of estimates	[2]	(508)	(18,182)
ARO liability, March 31:		70,043	70,759
Less current portion		3,243	3,499
Total long-term ARO		$ 66,800	$ 67,260

[1] We sold our interest in a number of non-core wells to unaffiliated third-parties during the first three months of 2017 and 2016, respectively.

[2] Plugging liability estimates were revised in both 2017 and 2016 for updates in the cost of services used to plug wells over the preceding year. We had various upward and downward adjustments.