Investment Securities - Schedule of Present Cost or Amortized Cost and Fair Values of Investments (Details) - USD ($) $ in Thousands |
Mar. 31, 2021 |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|---|
| Schedule Of Investments [Line Items] | |||
| Amortized cost | $ 695 | $ 694 | |
| Fair value | 703 | 737 | |
| Fair value | 34,798 | 53,963 | $ 56,428 |
| Amortized cost | 36,977 | 54,647 | 57,045 |
| Gross unrealized gains | 44 | 94 | 68 |
| Gross unrealized losses | (519) | (41) | |
| Fair value | 36,502 | 54,700 | 57,113 |
| U.S. government and government agencies and authorities | Investment securities, held-to-maturity | |||
| Schedule Of Investments [Line Items] | |||
| Amortized cost | 695 | 694 | 663 |
| Gross unrealized gains | 21 | 43 | 22 |
| Gross unrealized losses | (13) | ||
| Fair value | 703 | 737 | 685 |
| U.S. government and government agencies and authorities | Investment securities, available-for-sale | |||
| Schedule Of Investments [Line Items] | |||
| Amortized cost | 36,282 | 53,953 | 56,382 |
| Gross unrealized gains | 23 | 51 | 46 |
| Gross unrealized losses | (506) | (41) | |
| Fair value | $ 35,799 | $ 53,963 | $ 56,428 |