Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2016 USD ($) wells	Mar. 31, 2015 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
Wells sold | wells		1,000
ARO liability, January 1:		$ 98,297	$ 100,567
Accretion of discount		879	932
Liability incurred		90	5,174
Liability settled		(375)	(760)
Liability sold	[1]	(9,950)	(240)
Revision of estimates	[2]	(18,182)	(10,232)
ARO liability, March 31:		70,759	95,441
Less current portion		3,499	3,467
Total long-term ARO		$ 67,260	$ 91,974

[1] We sold approximately 1,000 wells to unaffiliated third-parties during the first quarter of 2016.

[2] 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.