Borrowings - Maximum aggregate balance of federal funds purchased and repurchase agreements (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Debt Disclosure [Abstract] | ||
| Maximum aggregate balance outstanding at any month-end | $ 195,498 | $ 281,833 |
| Average montly aggregate balance outstanding | $ 143,718 | $ 222,565 |
| Weighted average interest rate for the year | 1.63% | 2.64% |
| Weighted average interest rate at December 31 | 1.11% | 2.50% |