Oil and Gas Properties (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended					6 Months Ended		12 Months Ended
	Feb. 28, 2010	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Jun. 30, 2010	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2007	Dec. 31, 2010
Oil and gas property impairments				$ 22,721,000	$ 159,862,000	$ 7,000,000	$ 22,721,000	$ 170,974,000
Oil and gas properties				6				15
Asset retirement obligation				230,807,000			230,807,000			234,936,000
Capitalized exploration cost				3,600,000			3,600,000
Working interest in oil and gas field									100.00%
Cash acquired from acquisition	10,200,000
Acquired working interest	50.00%
Approximate gain on acquisition	6,000,000
Working interest before acquisition						50.00%
Hurricane-related repair costs					1,600,000		100,000	3,600,000
Insurance reimbursements							4,700,000
General Insurance Expense		2,000,000	8,400,000
Prepaid Insurance				12,141,000			12,141,000			12,375,000
Hurricane Catastrophic Bond [Member]
Prepaid Insurance				10,600,000			10,600,000
Non-Domestic Oil and Gas Property [Member]
Oil and gas property impairments						4,100,000	4,100,000
Asset retirement obligation				12,100,000			12,100,000
Accrued reclamation costs, current				$ 3,700,000			$ 3,700,000