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Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Thousands |  | 3 Months Ended |  |
--- | --- | --- | --- | ---
Oct. 19, 2020 | Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Commitments And Contingencies [Line Items] |  |  |  |  |
Allowance for credit loss |  | $ 49,828 | $ 43,356 | $ 52,420 | $ 30,482
Statute of limitations period | 3 years |  |  |  |
New York [Member] |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |
Statute of limitations period | 6 years |  |  |  |
Unfunded Commitments [Member] |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |
Credit loss expense |  | (276) | $ 1,000 |  |
Unfunded Commitments [Member] | Other Liabilities [Member] |  |  |  |  |
Commitments And Contingencies [Line Items] |  |  |  |  |
Allowance for credit loss |  | $ 2,900 |  | $ 3,100 |

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