Disclosures about Fair Value of Financial Instruments - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets:
Short-term derivative instruments	$ 83,262	$ 80,911
Long-term derivative instruments	25,839	70,805
Liabilities:
Short-term derivative instruments	(34,518)	(29,326)
Long-term derivative instruments	(15,142)	(31,275)
Commodity Derivative Contracts
Assets:
Short-term derivative instruments	83,262	80,911
Long-term derivative instruments	25,839	70,805
Total derivative instrument - asset	109,101	151,716
Liabilities:
Short-term derivative instruments	(34,518)	(29,326)
Long-term derivative instruments	(15,142)	(31,275)
Total derivative instruments - liability	(49,660)	(60,601)
Net commodity derivative asset	59,441	91,115
Commodity Derivative Contracts | Level 2
Assets:
Short-term derivative instruments	83,262	80,911
Long-term derivative instruments	25,839	70,805
Total derivative instrument - asset	109,101	151,716
Liabilities:
Short-term derivative instruments	(34,518)	(29,326)
Long-term derivative instruments	(15,142)	(31,275)
Total derivative instruments - liability	(49,660)	(60,601)
Net commodity derivative asset	$ 59,441	$ 91,115