Fair Value Measurements (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Fair Value Measurements (Textuals) [Abstract]
Interest and dividends	$ 60,000	$ 39,000	$ 95,000	$ 71,000
Mark-to-market gain (loss)	5,000	3,200,000	1,300,000	3,800,000
Oil and gas property impairment				6,505,000
Allowance for uncollectible receivables	3,800,000		3,800,000		5,000,000
Number of financial institutions included in counterparties			10
Number of secured lenders in bank credit facility			9
Net derivative receivable	$ 6,900,000		$ 6,900,000
6.375% Senior Subordinated Notes due 2015 [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	6.375%		6.375%		6.375%
7.5% senior subordinated notes due 2016, net of discount [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	7.50%		7.50%		7.50%
7.5% Senior Subordinated Notes due 2017 [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	7.50%		7.50%		7.50%
7.25% Senior Subordinated Notes due 2018 [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	7.25%		7.25%		7.25%
8.0% senior subordinated notes due 2019, net of discount [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	8.00%		8.00%		8.00%
6.75% Senior Subordinated Notes due 2020 [Member]
Debt Instrument [Line Items]
Interest Rate on Senior Subordinated Notes	6.75%		6.75%		6.75%