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Amount of gain (loss) on sale or disposal of proven and unproven oil and gas properties.

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Oil and gas properties net of accumulated depreciation, depletion, amortization, impairment, and abandonment, carried under the successful effort method.

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The net cash paid (received) associated with the acquisition or disposal of all investments, including securities and other assets.

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DIVESTITURES (Narrative) (Details) - USD ($) shares in Millions			1 Months Ended									3 Months Ended		4 Months Ended	5 Months Ended	6 Months Ended	7 Months Ended	12 Months Ended
	Apr. 10, 2017	Apr. 05, 2017	Mar. 31, 2020	Dec. 31, 2019	Nov. 30, 2019	Sep. 30, 2019	Apr. 30, 2019	Jan. 31, 2019	Dec. 31, 2018	Aug. 31, 2018	Aug. 31, 2017	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2019	May 31, 2018	Jun. 30, 2020	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2017	Jun. 01, 2018
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties													$ 129,100,000		$ 3,000		$ 3,065,000	$ 129,082,000	$ 93,607,000
Proceeds from sale of oil and natural gas properties															3,000		140,324,000	119,750,000	3,654,000
Oil and natural gas properties, net				$ 114,031,000					$ 405,688,000			$ 114,031,000		$ 114,031,000	1,355,504,000		405,688,000	114,031,000		$ 616,018,000
Proceeds from sale of property, plant, and equipment																		700,000
Gain (loss) on disposition of oil and gas property															(5,000)		697,000	318,000	981,000
Gain (loss) on disposition of property plant equipment																		100,000
Assets held for sale				316,000								316,000		316,000				316,000
Liabilities related to assets held for sale				139,000								139,000		139,000				139,000
Accounts receivable – other				1,322,000					4,496,000			1,322,000		1,322,000	800,000		4,496,000	1,322,000		800,000
Accounts payable and accrued liabilities				23,524,000					26,146,000			23,524,000		23,524,000	$ 34,922,000		26,146,000	23,524,000		$ 36,787,000
Mid Continent Area Oil and Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		6,700,000
Accounts payable and accrued liabilities						$ 400,000
Remaining Mid Continent Area Oil And Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		4,900,000
Proceeds from sale of oil and natural gas properties												700,000
Barnett Shale [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		78,100,000
Liabilities related to assets held for sale				100,000								100,000		100,000				100,000
Remaining Barnett Shale [Member]
Significant Acquisitions and Disposals [Line Items]
Assets held for sale				100,000								100,000		100,000				100,000
Ohio and Pennsylvania Oil and Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties	$ 0
Proceeds from sale of oil and natural gas properties	1,100,000
Gain (loss) on disposition of oil and gas property	$ 0
East Texas Oil and Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																			$ 2,900,000
Proceeds from sale of oil and natural gas properties		$ 600,000
San Juan Property [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		25,400,000
Proceeds from sale of oil and natural gas properties							$ 36,800,000
Accounts receivable – other							$ 300,000
San Juan Property [Member] \| Land [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from sale of property, plant, and equipment											$ 1,000,000
Gain (loss) on disposition of property plant equipment											$ 1,000,000
Monroe Field Property [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		2,100,000
Accounts receivable – other					$ 200,000
Permian Basin Property [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		8,000,000
Proceeds from sale of oil and natural gas properties				2,900,000
Assets held for sale				200,000								200,000		200,000				200,000
Liabilities related to assets held for sale				$ 100,000								$ 100,000		100,000				100,000
Michigan Oil And Natural Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		8,800,000
Proceeds from sale of oil and natural gas properties			$ 4,800,000
Scenario, Forecast \| Remaining Barnett Shale [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from sale of oil and natural gas properties																$ 100,000
Scenario, Forecast \| Remaining Permian Basin Property [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from sale of oil and natural gas properties																$ 100,000
Magnolia Oil Gas Parent LLC And Magnolia Oil Gas Corporation [Member]
Significant Acquisitions and Disposals [Line Items]
Business acquisition equity interests issued or issuable number of shares originally acquired then sold								4.2
Proceeds from sale of available-for-sale securities, equity								$ (51,700,000)
Proceeds from sale of property, plant, and equipment										$ 1,400,000
Magnolia Oil Gas Parent LLC And Magnolia Oil Gas Corporation [Member] \| Central Texas And Karnes County Oil And Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Shares issued by acquirer										4.2
Total consideration received based on closing price of shares, net of preliminary purchase price adjustments										$ 192,700,000
Impairment of oil and natural gas properties																	2,900,000
Proceeds from sale of oil and natural gas properties										134,400,000
Third Party Acquirer [Member] \| Central Texas Oil And Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																	$ 200,000
Proceeds from sale of oil and natural gas properties									2,600,000	$ 3,400,000
Gain (loss) on disposition of oil and gas property									700,000
Third Party Acquirer [Member] \| Mid Continent Area Oil and Gas Properties [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties						200,000		0	0									1,800,000
Proceeds from sale of oil and natural gas properties						$ 4,900,000			1,000,000				2,200,000
Proceeds from sale of property, plant, and equipment								1,800,000
Gain (loss) on disposition of oil and gas property								$ 0	$ 0
Preferential rights to purchase that were exercised by other working interest owners													$ 900,000
Third Party Acquirer [Member] \| Barnett Shale [Member]
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and natural gas properties																		$ 78,100,000
Proceeds from sale of oil and natural gas properties														$ 68,400,000
Maximum \| Monroe Field Property [Member]
Significant Acquisitions and Disposals [Line Items]
Proceeds from sale of oil and natural gas properties					$ 100,000