Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Payable and Accrued Expenses (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Accrued Drilling Costs
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	$ 189,749	$ 241,298
Revenue and Severence Taxes Payable
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	61,613	37,066
Accrued Lease Operating Expense
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	25,197	17,643
Joint Owner Advances
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	79,138	24,698
Accrued Compensation Costs
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	43,056	45,235
Plugging and Abandonment Liability
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	7,462	11,679
Accrued Interest Payable
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	14,646	2,582
Other Current Liabilities
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	36,138	37,453
Total Current Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Expenses
Accounts Payable and Accrued Liabilities	$ 456,999	$ 417,654