Derivative Financial Instruments - Summary of Pre-tax Realized and Unrealized Gain (Loss) Recognized Related to Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Derivative [Line Items]
Unrealized loss on commodity derivatives	$ (7,606)	$ (13,218)
Loss on commodity derivatives	(6,530)	(13,218)
Commodity Derivative Contract
Derivative [Line Items]
Unrealized loss on commodity derivatives	(7,606)	(13,218)
Loss on commodity derivatives	(6,530)	$ (13,218)
Commodity Derivative Contract \| Natural Gas
Derivative [Line Items]
Realized gain (loss) on commodity derivatives	1,446
Commodity Derivative Contract \| Oil
Derivative [Line Items]
Realized gain (loss) on commodity derivatives	$ (370)

The realized and unrealized gain (loss) on commodity derivatives relating to actual amounts received or paid under the respective contracts and the realized and unrealized gain or loss on commodity derivative contracts representing the change in the fair market value of derivative instruments that have not actually settled.

No definition available.

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- Definition

Actual amounts received or paid related to natural gas derivative instruments, including options, swaps, futures, and forward contracts, which were included in earnings in the period.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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