Quarterly report [Sections 13 or 15(d)]

Fair Value Measurements - Fair Value on a Recurring Basis (Details)

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Fair Value Measurements - Fair Value on a Recurring Basis (Details) - USD ($)
 9 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Dec. 31, 2024
Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized gain (loss) on investment securities $ (74,995) $ 0    
Fair Value, Measurements, Recurring        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized gain (loss) on investment securities (74,995) 0    
Fair Value, Measurements, Recurring | Level 1        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets, Fair Value Disclosure 0 0    
Fair Value, Measurements, Recurring | Level 2        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets, Fair Value Disclosure 18,749 93,744    
Fair Value, Measurements, Recurring | Level 3        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets, Fair Value Disclosure 0 0    
Estimate of Fair Value Measurement | Fair Value, Measurements, Recurring        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets, Fair Value Disclosure 18,749 93,744 $ 93,744 $ 93,744
Eurosite Power, Inc. | Fair Value, Measurements, Recurring        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized gain (loss) on investment securities (74,995) 0    
Eurosite Power, Inc. | Fair Value, Measurements, Recurring | Level 1        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Available-for-sale equity securities 0 0    
Eurosite Power, Inc. | Fair Value, Measurements, Recurring | Level 2        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Available-for-sale equity securities 18,749 93,744    
Eurosite Power, Inc. | Fair Value, Measurements, Recurring | Level 3        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Available-for-sale equity securities 0 0    
Eurosite Power, Inc. | Estimate of Fair Value Measurement | Fair Value, Measurements, Recurring        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Available-for-sale equity securities $ 18,749 $ 93,744