Supplemental Oil and Gas Information (Unaudited) (Changes In Proved Reserve Quantities) (Details)	12 Months Ended
	Dec. 31, 2012 Mcf		Dec. 31, 2011 Mcf
Gas (Mcf) [Member]
Reserve Quantities [Line Items]
Balance	1,230,700		1,840,800
Revisions	(278,800)	[1]	(333,800)	[2]
Production	(326,800)		(276,300)
Balance	625,100		1,230,700
Oil (Bbls) [Member]
Reserve Quantities [Line Items]
Balance	3,800		5,200
Revisions	1,200	[1]	500	[2]
Production	(1,800)		(1,900)
Balance	3,200		3,800

[1] (2) The downward revision in natural gas volumes is primarily due to a decline in SEC base pricing from the prior year, a decrease in the positive gas price basis differentials and a decrease in economic lives resulting from increased expenses.

[2] (1) The change in estimate of natural gas reserves in 2011 was due to actual production not meeting engineering expectations. The increase in the estimate of oil reserves for 2011 was due to actual production outperforming engineering expectations.