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Financial Instruments Measured at Fair Value and Concentrations of Credit Risk - Summary of Fair Value Measurements and Financial Statement Presentation (Detail) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
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Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | $ 3,311 | $ 12,165
Short Term Investments [Member] |  |
Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | 3,045 | 11,698
Commodity Derivative Contracts [Member] |  |
Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | 266 | 467
Level 1 [Member] |  |
Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | 3,311 | 12,165
Level 1 [Member] | Short Term Investments [Member] |  |
Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | 3,045 | 11,698
Level 1 [Member] | Commodity Derivative Contracts [Member] |  |
Fair Value Concentration Of Risk Financial Statement Captions [Line Items] |  |
Fair Values of Assets | $ 266 | $ 467

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