SUPPLEMENTAL DISCLOSURES ABOUT NATURAL GAS PRODUCING ACTIVITIES - Natural Gas & Condensate Reserve Quantity Information (Details) MMcfe in Thousands, MMcf in Thousands, MBbls in Thousands	12 Months Ended
Dec. 31, 2019 MMcfe Bcfe MBbls MMcf	Dec. 31, 2018 MMcfe Bcfe MBbls MMcf	Dec. 31, 2017 MMcfe Bcfe MBbls MMcf
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Extensions, discoveries and other additions \| Bcfe	13	85
Revisions of previous estimates \| Bcfe	4	22
Purchases of reserves-in-place \| Bcfe		1	327
Gas
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves, beginning balance \| MMcf	264,854	327,118	0
Extensions, discoveries and other additions \| MMcf	12,848	22,481	0
Revisions of previous estimates \| MMcf	4,737	(84,061)	0
Production \| MMcf	(13,901)	(1,399)	(190)
Sale of reserves-in-place \| MMcf	0	0	0
Purchases of reserves-in-place \| MMcf	0	715	327,308
Proved reserves, ending balance \| MMcf	268,538	264,854	327,118
Proved developed reserves: \| MMcf	30,699	17,522	5,720
Proved undeveloped reserves: \| MMcf	237,839	247,332	321,398
Condensate
Proved Developed and Undeveloped Reserves [Roll Forward]
Proved reserves, beginning balance \| MBbls	7	10	0
Extensions, discoveries and other additions \| MBbls	0	0	0
Revisions of previous estimates \| MBbls	(6)	(2)	0
Production \| MBbls	(1)	(1)	0
Sale of reserves-in-place \| MBbls	0	0	0
Purchases of reserves-in-place \| MBbls	0	0	10
Proved reserves, ending balance \| MBbls	0	7	10
Proved developed reserves: \| MBbls	0	7	10
Proved undeveloped reserves: \| MBbls	0	0	0
Gas Equivalent
Proved Developed and Undeveloped Reserve (Energy) [Roll Forward]
Proved reserve (energy), beginning balance \| MMcfe	264,899	327,180	0
Extensions, discoveries and other additions \| MMcfe	12,848	22,481	0
Revisions of previous estimates \| MMcfe	4,696	(84,072)	0
Production \| MMcfe	(13,905)	(1,405)	(191)
Sale of reserves-in-place \| MMcfe	0	0	0
Purchases of reserves-in-place \| MMcfe	0	715	327,371
Proved reserve (energy), ending balance \| MMcfe	268,538	264,899	327,180
Proved developed reserves: \| MMcfe	30,699	17,567	5,782
Proved undeveloped reserves: \| MMcfe	237,839	247,332	321,398

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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Energy measure of proved reserve of oil and gas, 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/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Energy measure of decrease in quantity of proved reserve of oil and gas resulting from production, 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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-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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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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-Subsection Instruction 2

Reference 2: 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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Form 20-F
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-Subsection Instruction 2

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Form 20-F
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

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Production of proved reserves.

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Purchase of minerals in place.

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Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.

+ References

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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
-Publisher SEC
-Name Form 20-F
-Section Item 18
-Subsection Instruction 2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Sales of minerals in place.

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-Name Form 20-F
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-Subsection Instruction 2

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Energy measure of interests in proved developed reserves of crude oil, including condensate and natural gas liquids, natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas.

+ References

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Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

+ References

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Energy measure of proved undeveloped reserves of crude oil, including condensate and natural gas liquids, natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas.

+ References

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Net quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other renewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves.

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