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Loans (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($) contract | Dec. 31, 2019 USD ($) contract | Dec. 31, 2018 contract
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Accrued Interest Receivable for Loans |  | $ 46,839 |
Financing Receivable Modifications Additional Commitment To Lend | $ 651 | $ 1,100 |
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | contract | 0 | 1 | 0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default |  | $ 26 |
Loan modifications, short-term deferments not classified as TDR, Number of contracts | contract | 70 |  |
Loan modifications, short-term deferments not classified as TDR, net of unearned income | $ 146,700 |  |
Paycheck Protection Program (PPP) loans, net of unearned income | 651,600 |  |
Loans Receivable |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans pledged to collateralize Federal Home Loan Bank Advances | 3,460,000 | 3,240,000 |
Commercial Loan |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Loans pledged to collateralize Federal Reserve Bank Borrowings | 200,400 | 151,300 |
Loans |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Accrued Interest Receivable for Loans | $ 37,800 | $ 33,000 |

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