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Derivatives, Hedging Activities and Financial Instruments with Off-Balance Sheet Risk - Commitments (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | $ 15,458,000 |  |  | $ 16,801,000
Provision for Unfunded Commitments | 980,000 | $ 734,000 | $ 2,500,000 |
Fixed [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 685,000 |  |  | 910,000
Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 14,773,000 |  |  | 15,891,000
Commitments to Extend Credit to Borrowers [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 15,391,000 |  |  | 16,734,000
Commitments to Extend Credit to Borrowers [Member] | Fixed [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 685,000 |  |  | 910,000
Commitments to Extend Credit to Borrowers [Member] | Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 14,706,000 |  |  | 15,824,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 9,210,000 |  |  | 9,951,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] | Fixed [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 329,000 |  |  | 339,000
Commitments to Extend Credit to Borrowers [Member] | Financial Standby Letter of Credit [Member] | Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 8,881,000 |  |  | 9,612,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 6,181,000 |  |  | 6,783,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] | Fixed [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 356,000 |  |  | 571,000
Commitments to Extend Credit to Borrowers [Member] | Performance Guarantee [Member] | Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 5,825,000 |  |  | 6,212,000
Commitments to Extend Credit Nonborrowers [Member] | Performance Guarantee [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 67,000 |  |  | 67,000
Commitments to Extend Credit Nonborrowers [Member] | Performance Guarantee [Member] | Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Total letters of credit | 67,000 |  |  | 67,000
Letter of Credit [Member] | Unused lines of Credit [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Loan commitments | 419,037,000 |  |  | 431,468,000
Letter of Credit [Member] | Unused lines of Credit [Member] | Fixed [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Loan commitments | 93,875,000 |  |  | 111,348,000
Letter of Credit [Member] | Unused lines of Credit [Member] | Variable [Member] |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Loan commitments | $ 325,162,000 |  |  | $ 320,120,000
Revision of Prior Period, Adjustment [Member] | Accounting Standards Update 2016-13 |  |  |  |
Company's contractual commitments due to letters of credit |  |  |  |
Provision for Unfunded Commitments |  |  | $ 1,700,000 |

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