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Investments - Clean Coal Investments - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2022 USD ($) Entities Plant | Dec. 31, 2021 USD ($)
Chem-Mod LLC [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Number of clean coal production plants owned | Plant | 35 |
Chem-Mod LLC [Member] | 2009 Era Plants [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Number of clean coal production plants owned | Plant | 14 |
Chem-Mod LLC [Member] | 2011 Era Plants [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Number of clean coal production plants owned | Plant | 21 |
Clean-Coal Investments [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Number of variable interest entities | Entities | 1 |
Clean-Coal Investments [Member] | VIE [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Total assets of limited liability companies | $ 35,300,000 |
Total liability of limited liability companies | $ 35,300,000 |
Total revenues of limited liability companies |  | $ 0
Total expenses of limited liability companies |  | $ 300,000

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