| Summary of Significant Accounting Policies - Interest income (Details) - USD ($) | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | |
| Summary of Significant Accounting Policies | |||
| Interest income arises on cash, cash equivalents and available-for-sale debt securities and is net of amortization (accretion) of the premium (discount) on purchase of the debt securities | $ (1,407,000) | $ (1,986,000) | |
| Interest income arises on cash, cash equivalents and available-for-sale debt securities and is net of amortization (accretion) of the premium (discount) on purchase of the debt securitiess | $ 2,525,000 | ||
| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Amount of accretion of purchase discount on nonoperating securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of amortization of purchase premium on nonoperating securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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