Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:	$ 146,159		$ 96,446
Accretion of discount	4,152		3,215
Liability incurred	3,820		52,306
Liability settled	(4,071)		(1,606)
Revision of estimates	(16,166)	[1]	(4,254)	[1]
ARO liability, September 30:	133,894		146,107
Less current portion	2,954		2,857
Total long-term ARO	$ 130,940		$ 143,250

[1] Plugging liability estimates were revised in both 2013 and 2012 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.