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Derivative Instruments - Schedule of Outstanding Commodity Derivative Instruments (Details) $ in Thousands	1 Months Ended	9 Months Ended
	Oct. 31, 2018 MMBTU $ / bbl $ / MMBTU bbl	Sep. 30, 2018 USD ($) MMBTU $ / bbl $ / MMBTU bbl
Derivative [Line Items]
Fair value asset | $		$ (213,146)
Crude Oil [Member] | 2018 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		3,761,000
Average swap price (in dollars per barrel)		52.95
Fair value asset | $		$ (71,621)
Crude Oil [Member] | 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		152,000
Average swap price (in dollars per barrel)		9.84
Fair value asset | $		$ 81
Crude Oil [Member] | 2018 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		517,000
Average floor price (in dollars per barrel)		58.74
Average ceiling price (in dollars per barrel)		63.94
Fair value asset | $		$ (5,171)
Crude Oil [Member] | 2019 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		5,613,000
Average swap price (in dollars per barrel)		53.33
Fair value asset | $		$ (99,347)
Crude Oil [Member] | 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		424,000
Average swap price (in dollars per barrel)		9.68
Fair value asset | $		$ 408
Crude Oil [Member] | 2019 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		3,223,000
Average floor price (in dollars per barrel)		57.99
Average ceiling price (in dollars per barrel)		75.46
Fair value asset | $		$ (7,580)
Crude Oil [Member] | 2019 Three-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		3,368,000
Average sub-floor price (in dollars per barrel)		40.54
Average floor price (in dollars per barrel)		51.03
Average ceiling price (in dollars per barrel)		68.68
Fair value asset | $		$ (21,771)
Crude Oil [Member] | 2020 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		403,000
Average swap price (in dollars per barrel)		53.47
Fair value asset | $		$ (5,911)
Crude Oil [Member] | 2020 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		279,000
Average floor price (in dollars per barrel)		57.78
Average ceiling price (in dollars per barrel)		76.13
Fair value asset | $		$ (273)
Crude Oil [Member] | 2020 Three-way Collars [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl		279,000
Average sub-floor price (in dollars per barrel)		40.00
Average floor price (in dollars per barrel)		50.56
Average ceiling price (in dollars per barrel)		67.80
Fair value asset | $		$ (1,778)
Natural Gas [Member] | 2018 Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU		3,496,000
Average swap price (in dollars per barrel) | $ / MMBTU		3.01
Fair value asset | $		$ (104)
Natural Gas [Member] | 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU		1,225,000
Average swap price (in dollars per barrel)		0.05
Fair value asset | $		$ (64)
Natural Gas [Member] | 2019 Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU		1,896,000
Average swap price (in dollars per barrel) | $ / MMBTU		2.95
Fair value asset | $		$ 16
Natural Gas [Member] | 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU		2,715,000
Average swap price (in dollars per barrel)		0.05
Fair value asset | $		$ (31)
Subsequent Event [Member] | Crude Oil [Member]
Derivative [Line Items]
Average floor price (in dollars per barrel)	64.05
Addition (reduction) in weighted average differential prices	(7.50)
Subsequent Event [Member] | Crude Oil [Member] | 2018 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl	213,000
Subsequent Event [Member] | Crude Oil [Member] | 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	60,000
Subsequent Event [Member] | Crude Oil [Member] | 2019 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl	792,000
Subsequent Event [Member] | Crude Oil [Member] | 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	424,000
Subsequent Event [Member] | Crude Oil [Member] | 2020 Swaps [Member]
Derivative [Line Items]
Total notional amount of oil (in Bbls) | bbl	62,000
Subsequent Event [Member] | Natural Gas [Member]
Derivative [Line Items]
Average floor price (in dollars per barrel) | $ / MMBTU	2.88
Addition (reduction) in weighted average differential prices | $ / MMBTU	0.13
Subsequent Event [Member] | Natural Gas [Member] | 2018 Basis Swaps [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	610,000
Subsequent Event [Member] | Natural Gas [Member] | 2018 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	305,000
Subsequent Event [Member] | Natural Gas [Member] | 2019 Basis Swaps [Member] [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	1,810,000
Subsequent Event [Member] | Natural Gas [Member] | 2019 Two-way Collars [Member]
Derivative [Line Items]
Total notional amount of natural gas (in MMBtu) | MMBTU	1,825,000

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- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13433-108611

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- Definition

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

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