Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:	$ 133,657		$ 146,159
Accretion of discount	1,215		1,521
Liability incurred	635		899
Liability settled	(548)		(1,519)
Liability sold	(459)		(169)
Revision of estimates	(14,600)	[1]	(11,299)	[1]
ARO liability, March 31:	119,900		135,592
Less current portion	2,961		2,917
Total long-term ARO	$ 116,939		$ 132,675

[1] Plugging liability estimates were revised in both three months ended March 31, 2014 and 2013 for updates in the cost of services used to plug wells over the preceding year. We had various upward and downward adjustments.