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Summary of Significant Accounting Policies (New Accounting Standards and Interpretations) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for credit loss | $ 86,833 | $ 106,246 | $ 136,589 | $ 218,011 |  | $ 3,025 | $ 2,271 | $ 1,986 | $ 1,651 | $ 968
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for credit loss | $ 8,300 |  |  |  | $ 8,300 |  |  |  |  |
Cumulative Effect, Period of Adoption, Adjustment | Purchased Credit Deteriorated Loans |  |  |  |  |  |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |  |  |  |  |  |
Allowance for credit loss |  |  |  |  | $ 62,600 |  |  |  |  |

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