Accounts Receivable and Accounts Payable and Accrued Expenses Accounts Receivable (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$ 318,371	$ 254,805
Accrued oil, gas, and NGL production revenue
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	228,169	160,568
Amounts due From Joint Interest Owner
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	37,517	42,740
Acquisition and Development Agreement receivable
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	0	19,931
State severance tax refunds
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	29,213	17,237
Other
Accounts, Notes, Loans and Financing Receivable
Accounts Receivable, Net, Current	$ 23,472	$ 14,329