Supplemental Oil And Natural Gas Information - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018 Bcfe	Dec. 31, 2017 Bcfe Well	Dec. 31, 2016 Bcfe
Reserve Quantities [Line Items]
Extensions	558.1	405.1	196.1
Revisions	(42.8)	695.6	14.8
Revisions due to (reductions) improvements in SEC pricing	15.0	607.2	(50.8)
Revisions due to changes in differentials	6.8	61.4	(17.9)
Revision due to outperforming previous estimate	67.5	69.6	83.5
Acquisition of proved developed and proved undeveloped leasehold acreage	16.3	1.9	4.1
Divestiture of proved developed and proved undeveloped leasehold acreage	0.2		10.7
Developments	148.3
Revisions offset due to decision to not develop certain proved, undeveloped reserves within five years		42.6
Revisions offset due to change in well spacing	(98.0)
Revisions offset due to change in five year development plan	(34.1)
Discount Rate [Member] \| Valuation Technique, Discounted Cash Flow [Member]
Reserve Quantities [Line Items]
Discount rate	10
Utica [Member]
Reserve Quantities [Line Items]
Developments		361.0
Number of nonproductive development wells \| Well		1
Utica [Member] \| Non-operated Well [Member]
Reserve Quantities [Line Items]
Developments		0.3
Utica [Member] \| Operated Assets [Member]
Reserve Quantities [Line Items]
Developments	398.2
Ohio Marcellus [Member]
Reserve Quantities [Line Items]
Developments		43.8
Number of productive development wells \| Well		3
Marcellus Shale [Member] \| Operated Assets [Member]
Reserve Quantities [Line Items]
Developments	11.6

Proved developed and undeveloped reserve previous estimate energy.

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Proved developed and undeveloped reserves revisions due to differential changes.

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Proved developed and undeveloped reserves revisions due to (reductions) improvements in pricing.

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Proved developed and undeveloped reserves revisions offset due to change in five year development plan

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Proved developed and undeveloped reserves revisions offset due to change in well spacing.

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Proved developed and undeveloped reserves revisions offset due to non-development of reserves within five years.

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Energy measure of increase in quantity of proved reserve of oil and gas resulting from the extension of the proved acreage of previously discovered reservoir or discovery of new field with proved reserve or of new reservoir of proved reserve in old field, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

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-Publisher SEC
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Energy measure of increase in quantity of proved reserve of oil and gas resulting from application of improved recovery techniques, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

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Energy measure of increase in quantity of proved reserve of oil and gas resulting from purchase of mineral in place, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Energy measure of increase (decrease) in quantity of proved reserve of oil and gas related to revision of a previous estimate resulting from new information, except for an increase in proved acreage, or change in economic factors, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

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Energy measure of decrease in quantity of proved reserve of oil and gas resulting from sale of mineral in place, stated in a unit of energy. For example, but not limited to, barrel of oil equivalents (BOE) or one thousand cubic feet of natural gas equivalent (Mcfe).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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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Value of input used to measure alternative investment.

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-SubTopic 10
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The number of nonproductive development wells (dry wells) drilled in the geographic area. A dry well (hole) is a well found to be incapable of producing either oil or gas in sufficient quantities to justify completion as an oil or gas well. The number of wells drilled refers to the number of wells (holes) completed at any time during the fiscal years, regardless when drilling was initiated.

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-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1205
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The number of productive developmental wells drilled in the geographic area. A productive well is a well that is not a dry well. The number of wells drilled refers to the number of wells (holes) completed at any time during the fiscal years, regardless when drilling was initiated.

+ References

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