Investment securities available for sale - Summary of gross realized gains and losses to available for sale securities (Details) - USD ($) |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2021 |
Mar. 31, 2020 |
Dec. 31, 2020 |
|
| Investment securities available for sale | |||
| Gross realized gains | $ 0 | $ 39,000 | |
| Gross realized losses | 0 | (27,000) | |
| Available-for-sale Securities, Gross Realized Gain (Loss), Total | $ 0 | $ 12,000 | $ 12,000 |