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Derivatives, Hedges and Financial Instruments - Additional Information (Detail)
$ / shares in Units, MMBTU in Millions
3 Months Ended 12 Months Ended
Sep. 30, 2021
USD ($)
Jun. 30, 2021
USD ($)
Mar. 31, 2021
USD ($)
Dec. 31, 2020
USD ($)
$ / shares
$ / MMBTU
Sep. 30, 2020
USD ($)
Jun. 30, 2020
USD ($)
Mar. 31, 2020
USD ($)
Dec. 31, 2021
USD ($)
MMBTU
$ / MMBTU
Dec. 31, 2020
USD ($)
MMBTU
$ / shares
$ / MMBTU
shares
Dec. 31, 2019
USD ($)
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Gain (loss) on sale of natural gas               $ 2,700,000 $ (1,600,000) $ 0
Realized gain on sale of natural gas               6,800,000    
Unrealized loss on sale of natural gas                 (1,200,000)  
Fair value of embedded derivative, noncurrent liability       $ 1,000,000.0         1,000,000.0  
Realized loss on fair value of embedded derivative               (3,300,000)    
Unrealized gain (loss) on fair value of embedded derivative $ (1,106,000) $ (716,000) $ (436,000) $ (561,000) $ (141,000) $ 120,000 $ 637,000      
Level 3 transfer               0 0 0
Non-Operating Other Income and Expense [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Unrealized gain (loss) on fair value of embedded derivative               $ (2,300,000) $ 100,000 $ 500,000
Embedded Derivative [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Participating right in dividends and liquidating distributions expressed in number of common shares | shares                 303,646  
Embedded Derivative [Member] | Common Stock [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Common stock per share | $ / shares       $ 3.39         $ 3.39  
Natural Gas Purchase Commitments [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Natural gas purchase commitments volume | MMBTU               5.4    
Weighted average cost of natural gas per unit | $ / MMBTU               4.53    
Weighted average natural gas market value per unit | $ / MMBTU               3.87    
Realized gain on sale of natural gas               $ 1,500,000    
Natural Gas Purchase Commitments [Member] | Level 2 [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Natural gas purchase commitments volume | MMBTU                 7.3  
Weighted average cost of natural gas per unit | $ / MMBTU       2.65         2.65  
Weighted average natural gas market value per unit | $ / MMBTU       2.49         2.49  
Natural Gas Purchase Commitments [Member] | Natural Gas Current Asset [Member] | Level 2 [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Natural gas contracts, fair value disclosure       $ 100,000         $ 100,000  
Natural Gas Purchase Commitments [Member] | Natural Gas Current Liability [Member] | Level 2 [Member]                    
Derivative Instruments And Hedging Activities Disclosures [Line Items]                    
Natural gas contracts, fair value disclosure       $ 1,300,000         $ 1,300,000