Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) $ in Thousands		9 Months Ended
		Sep. 30, 2016 USD ($) wells	Sep. 30, 2015 USD ($)
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:		$ 98,297	$ 100,567
Accretion of discount		2,147	2,599
Liability incurred		311	6,505
Liability settled		(874)	(1,933)
Liability sold	[1]	(10,758)	(249)
Revision of estimates	[2]	(18,102)	(12,881)
ARO liability, September 30:		71,021	94,608
Less current portion		3,498	3,481
Total long-term ARO		$ 67,523	$ 91,127
Wells sold | wells		1,270

[1] We sold our interest in approximately 1,270 non-core wells to unaffiliated third-parties during the first nine months 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.