Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 70,170	$ 98,297
Accretion of discount		1,458	1,513
Liability incurred		1,018	212
Liability settled		(1,224)	(605)
Liability sold	[1]	(1,412)	(10,308)
Revision of estimates	[2]	39	(18,183)
ARO liability, June 30:		70,049	70,926
Less current portion		2,825	3,523
Total long-term ARO		$ 67,224	$ 67,403

[1] We sold our interest in a number of non-core wells to unaffiliated third-parties during the first six 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.