Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$ 322,630	$ 318,371
Accrued oil, gas, and NGL production revenue
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	180,250	228,169
Amounts due From Joint Interest Owner
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	58,347	37,517
Derivative Settlement Receivable [Member]
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	39,811	770
State severance tax refunds
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	24,394	29,213
Other
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$ 19,828	$ 22,702