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EQUITY INVESTMENTS (Narrative) (Details) a in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2020 USD ($) | Jun. 30, 2021 USD ($) a | Jun. 30, 2020 USD ($) | Dec. 31, 2019 USD ($) | May 17, 2021 USD ($) | Dec. 31, 2020 USD ($) | Mar. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Equity investments |  | $ 0 |  |  | $ 0 | $ 24,816,000 |
Investment in Grizzly Oil Sands ULC |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Equity investment, ownership interest |  | 24.50% |  |  |  |  |
Equity method investment, impairment |  | $ 0 | $ 0 |  |  |  |
Amount of cash paid for equity investments |  |  |  | $ 0 |  |  |
Increase (decrease) due to foreign currency translation adjustment | $ 6,900,000 |  | $ (7,800,000) |  |  |  |
Equity investments |  | $ 0 |  |  | $ 0 | 24,816,000 |
Investment in Mammoth Energy |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Equity investment, ownership interest |  | 0.00% |  |  |  |  |
Equity investments |  | $ 0 |  |  |  | $ 0 | $ 0
Athabasca, Peace River And Cold Lake Oil Sands Regions | Investment in Grizzly Oil Sands ULC |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Gas and oil area, reserve (in acres) | a |  | 830 |  |  |  |  |

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- Definition This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 35 -Paragraph 32 -URI http://asc.fasb.org/extlink&oid=124268079&loc=d3e32787-111569 + Details
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