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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Capitalized Costs Related to Oil and Gas Producing Activities (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
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Reserve Quantities [Line Items] |  |
Proved properties | $ 8,909,069 | $ 7,153,799
Unproved properties | 1,686,666 | 2,873,037
Capitalized costs, gross | 10,595,735 | 10,026,836
Accumulated depreciation, depletion, amortization and impairment | (7,191,957) | (4,613,293)
Net capitalized costs | 3,403,778 | 5,413,543
Investment in Grizzly Oil Sands ULC |  |
Reserve Quantities [Line Items] |  |
Proved properties | 64,476 | 67,475
Unproved properties | 85,395 | 79,605
Capitalized costs, gross | 149,871 | 147,080
Accumulated depreciation, depletion, amortization and impairment | (1,634) | (1,553)
Net capitalized costs | $ 148,237 | $ 145,527

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- Definition Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447 + Details
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- Definition The sum of capitalized costs relating to oil and gas producing activities before accounting for accumulated depreciation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447 + Details
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- Definition Net amount of capitalized costs relating to oil and gas producing activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447 + Details
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- Definition Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -URI http://asc.fasb.org/subtopic&trid=2145654 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447 + Details
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- Definition Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -URI http://asc.fasb.org/topic&trid=2145477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61901-109447 + Details
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