Summary of Significant Accounting Policies (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jan. 01, 2007
Summary of Significant Accounting Policies (Textual) [Abstract]
Total capitalized internal costs			$ 16,200,000	$ 14,400,000
Total capitalized interest cost on unproved properties	2,000,000	1,900,000	4,000,000	3,700,000
Discount rate for estimated future net revenues from proved properties	10.00%
Allowance for doubtful accounts receivable, current	100,000		100,000		100,000
Accounts receivable	51,878,000		51,878,000		64,392,000
Net gain (loss) related to derivative activities, recognized	(2,600,000)	(800,000)	(2,300,000)	(1,000,000)
Other Receivables, Net, Current	1,800,000		1,800,000
Percentage of working interest in wells			100.00%
Total amount of supervision fees charged to wells			5,800,000	6,600,000
Inventories carried at cost	5,000,000		5,000,000		3,600,000
Inventory Write-down			300,000	900,000
Decrease in retained earnings for uncertain tax positions						1,000,000
Outstanding checks included in trade accounts payable	23,700,000		23,700,000		18,700,000
Maturity time period for cash and cash equivalents			3 months
Restricted cash and cash equivalents included in other long term assets	1,000,000		1,000,000		1,300,000
Asset Retirement Obligation - current portion	9,656,000		9,656,000		9,279,000
Senior Notes Due Two Thousand Seven Teen [Member]
Debt Issuance Costs (Textual) [Abstract]
Senior notes, issued	250,000,000		250,000,000
Stated Rate of Senior notes	7.125%		7.125%
Balance of issuance costs for credit facility	2,400,000		2,400,000
Net accumulated amortization of debt issuance cost	1,700,000		1,700,000
Senior Notes Due Two Thousand Twenty [Member]
Debt Issuance Costs (Textual) [Abstract]
Senior notes, issued	225,000,000		225,000,000
Stated Rate of Senior notes	8.875%		8.875%
Balance of issuance costs for credit facility	4,200,000		4,200,000
Net accumulated amortization of debt issuance cost	900,000		900,000
Senior Notes Due 2022 [Member]
Debt Issuance Costs (Textual) [Abstract]
Senior notes, issued	250,000,000		250,000,000
Stated Rate of Senior notes	7.875%		7.875%
Balance of issuance costs for credit facility	4,600,000		4,600,000
Net accumulated amortization of debt issuance cost	200,000		200,000
Line of Credit [Member]
Debt Issuance Costs (Textual) [Abstract]
Balance of issuance costs for credit facility	3,100,000		3,100,000
Net accumulated amortization of debt issuance cost	4,400,000		4,400,000
Trade Accounts Receivable [Member]
Accounts Receivable (Textual) [Abstract]
Trade Accounts Receivable, Gross	40,700,000		40,700,000		54,700,000
Joint Interest Owners [Member]
Accounts Receivable (Textual) [Abstract]
Accounts receivable related to joint interest owners	3,000,000		3,000,000		4,200,000
Other Accounts Receivable [Member]
Accounts Receivable (Textual) [Abstract]
Other Receivables	8,200,000		8,200,000		5,600,000
Maximum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Property, Plant and Equipment, Useful Life			20 years
Minimum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Property, Plant and Equipment, Useful Life			2 years
Oil Floors [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Fair value of derivative instruments	$ 0		$ 0		$ 100,000