Basis of Presentation, Significant Accounting Policies, and Recently Issued Accounting Standards Basis of Presentation and Significant Accounting Policies - Other (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Inventory Disclosure [Abstract]
Raw Materials Inventory	$ 16,500,000	$ 22,500,000
Raw Materials Inventory Write-down	0	0	14,223,000
Property, Plant and Equipment [Abstract]
Property, Plant, and Equipment, Salvage Value	64,100,000	67,900,000
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets, Net (Excluding Goodwill)	7,100,000	4,400,000
Cash Settlement Balancing [Abstract]
Gas Balancing Receivable	1,900,000	1,500,000
Gas Balancing Payable	1,100,000	934,000
Revenues [Abstract]
Revenue Receipt, Days After Sale, Low End of Range	30
Revenue Receipt, Days After Sale, High End of Range	90
Major Customers [Abstract]
Percent of Revenue from Major Customers	18.00%	11.00%	12.00%
Impairment of Proved and Unproved Properties
Impairment of proved properties	219,037,000	6,127,000	174,813,000
Abandonment and impairment of unproved properties	$ 7,367,000	$ 1,986,000	$ 45,447,000