Summary of Significant Accounting Policies - Accrued Oil and Natural Gas Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenue payable	$ 15,660	$ 19,267
Accrued lease operating expense	17,861	21,177
Accrued capital expenditures	3,870	20,773
Accrued ad valorem tax	10,709	9,382
Other	6,567	8,016
Accrued oil and natural gas liabilities	$ 54,667	$ 78,615