Asset Retirement Obligations (Schedule Of Asset Retirement Obligations) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013
Asset Retirement Obligation Disclosure [Abstract]
ARO liability, January 1:	$ 133,657		$ 146,159
Accretion of discount	2,366		2,825
Liability incurred	1,900		2,869
Liability settled	(1,917)		(3,192)
Liability sold	(877)		(324)
Revision of estimates	(14,538)	[1]	(11,298)	[1]
ARO liability, June 30:	120,591		137,039
Less current portion	3,118		2,948
Total long-term ARO	$ 117,473		$ 134,091

[1] Plugging liability estimates were revised in both 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.