Disclosures about Fair Value of Financial Instruments - Schedule of Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Short-term derivative instruments	$ 32,537	$ 83,262
Long-term derivative instruments	21,017	25,839
Liabilities:
Short-term derivative instruments	(21,122)	(34,518)
Long-term derivative instruments	(12,465)	(15,142)
Commodity Derivative Contracts
Assets:
Short-term derivative instruments	32,537	83,262
Long-term derivative instruments	21,017	25,839
Total derivative instrument - asset	53,554	109,101
Liabilities:
Short-term derivative instruments	(21,122)	(34,518)
Long-term derivative instruments	(12,465)	(15,142)
Total derivative instruments - liability	(33,587)	(49,660)
Net commodity derivative asset	19,967	59,441
Commodity Derivative Contracts | Level 1
Assets:
Short-term derivative instruments	0	0
Long-term derivative instruments	0	0
Total derivative instrument - asset	0	0
Liabilities:
Short-term derivative instruments	0	0
Long-term derivative instruments	0	0
Total derivative instruments - liability	0	0
Net commodity derivative asset	0	0
Commodity Derivative Contracts | Level 2
Assets:
Short-term derivative instruments	32,537	83,262
Long-term derivative instruments	21,017	25,839
Total derivative instrument - asset	53,554	109,101
Liabilities:
Short-term derivative instruments	(21,122)	(34,518)
Long-term derivative instruments	(12,465)	(15,142)
Total derivative instruments - liability	(33,587)	(49,660)
Net commodity derivative asset	19,967	59,441
Commodity Derivative Contracts | Level 3
Assets:
Short-term derivative instruments	0	0
Long-term derivative instruments	0	0
Total derivative instrument - asset	0	0
Liabilities:
Short-term derivative instruments	0	0
Long-term derivative instruments	0	0
Total derivative instruments - liability	0	0
Net commodity derivative asset	$ 0	$ 0