Derivative Financial Instruments - Summary of Open Commodity Derivative Contracts (Details) bbl in Thousands, $ in Thousands, MMBTU in Millions	1 Months Ended	6 Months Ended
Jul. 24, 2018 MMBTU $ / MMBTU	Jun. 30, 2018 USD ($) MMBTU $ / MMBTU $ / bbl bbl
Derivative [Line Items]
Liability, Fair Value		$ (54,891)
Commodity Derivative Contract Fixed Price Swaps \| Crude Oil
Derivative [Line Items]
Type		Crude oil fixed price swaps
Commodity Derivative Contract Fixed Price Swaps \| Natural Gas
Derivative [Line Items]
Type		Natural gas fixed price swaps
Commodity Derivative Basis Swap Contracts \| Natural Gas
Derivative [Line Items]
Type		Natural gas basis swaps
Commodity Derivative Basis Swap Contracts \| Natural Gas \| Subsequent Event
Derivative [Line Items]
Type	Natural gas basis swaps
Commodity Derivative Basis Swap Contracts One \| Natural Gas \| Subsequent Event
Derivative [Line Items]
Year	2018 (August through October)
Index	NYMEX-Henry Hub
Total Volumes \| MMBTU	6.4
Weighted Average Price per Unit \| $ / MMBTU	(0.48)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps \| Crude Oil
Derivative [Line Items]
Year		2020
Index		NYMEX-WTI
Total Volumes \| bbl		90
Weighted Average Price per Unit \| $ / bbl		60.05
Liability, Fair Value		$ (204)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps \| Natural Gas
Derivative [Line Items]
Year		2020
Index		NYMEX-Henry Hub
Total Volumes \| MMBTU		15.5
Weighted Average Price per Unit \| $ / MMBTU		2.76
Liability, Fair Value		$ (2,662)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps Two \| Crude Oil
Derivative [Line Items]
Year		2019
Index		NYMEX-WTI
Total Volumes \| bbl		1,700
Weighted Average Price per Unit \| $ / bbl		58.83
Liability, Fair Value		$ (11,645)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps Two \| Natural Gas
Derivative [Line Items]
Year		2019
Index		NYMEX-Henry Hub
Total Volumes \| MMBTU		167.3
Weighted Average Price per Unit \| $ / MMBTU		2.85
Liability, Fair Value		$ (4,557)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps One \| Crude Oil
Derivative [Line Items]
Year		2018 (July through December)
Index		NYMEX-WTI
Total Volumes \| bbl		1,200
Weighted Average Price per Unit \| $ / bbl		60.53
Liability, Fair Value		$ (12,050)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Contract Fixed Price Swaps One \| Natural Gas
Derivative [Line Items]
Year		2018 (July through December)
Index		NYMEX-Henry Hub
Total Volumes \| MMBTU		141.1
Weighted Average Price per Unit \| $ / MMBTU		2.89
Liability, Fair Value		$ (9,430)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Basis Swap Contracts One \| Natural Gas
Derivative [Line Items]
Year		2018 (July through December)
Index		NW Rockies Basis Swap
Total Volumes \| MMBTU		94.6
Weighted Average Price per Unit \| $ / MMBTU		(0.68)
Liability, Fair Value		$ (3,176)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Basis Swap Contracts Two \| Natural Gas
Derivative [Line Items]
Year		2019
Index		NW Rockies Basis Swap
Total Volumes \| MMBTU		84.5
Weighted Average Price per Unit \| $ / MMBTU		(0.70)
Liability, Fair Value		$ (848)
Derivative Financial Instruments, Liabilities \| Commodity Derivative Basis Swap Contracts Three \| Natural Gas
Derivative [Line Items]
Year		2020
Index		NW Rockies Basis Swap

Derivative contract maturity peiod.

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Derivative maturity period.

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Derivative swap type average differential.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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.

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Nominal energy measure used to calculate payments on a derivative instrument.

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Nominal volume used to calculate payments on a derivative instrument.

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- Definition

Indicates whether the entity pays a variable or fixed price on a price risk swap.

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Average fixed price related to the group of price risk swap derivatives.

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- Definition

Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu).

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