Summary of Significant Accounting Policies - Interest income (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Summary of Significant Accounting Policies | |||
| Amortization (accretion) of the premium (discount) | $ 3,836,000 | $ (185,000) | $ 237,000 |
| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of accretion (amortization) of purchase discount (premium) on nonoperating securities. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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