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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Costs Incurred In Oil and Gas Property Acquisition and Development Activities (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] |  |  |
Acquisition | $ 124,558 | $ 1,951,281 | $ 152,887
Development | 603,676 | 994,237 | 423,998
Exploratory | 21,840 | 0 | 0
Recompletions | 7,915 | 14,289 | 16,386
Capitalized asset retirement obligation | 1,452 | 42,270 | 10,971
Total | 759,441 | 3,002,077 | 604,242
Investment in Grizzly Oil Sands ULC |  |  |
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] |  |  |
Acquisition | 238 | 503 | 357
Development | 0 | 0 | 0
Exploratory | 0 | 0 | 0
Capitalized asset retirement obligation | (285) | (524) | 784
Total | $ (47) | $ (21) | $ 1,141

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- Definition Cost incurred, including capitalized costs and costs charged to expense, in acquisition of oil and gas properties. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 18 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62014-109447 + Details
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- Definition Development costs incurred, including capitalized costs and costs charged to expense, in oil and gas 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 18 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62014-109447 + Details
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- Definition Exploration costs incurred, including capitalized costs and costs charged to expense, in oil and gas 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 18 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e62014-109447 + Details
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