Goodwill and intangible assets - Core Deposit and Other Intangibles (Details) - USD ($) $ in Thousands |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | $ 62,523 | $ 52,363 |
| Accumulated Amortization | (40,097) | (34,774) |
| Net Carrying Amount | 22,426 | 17,589 |
| Core deposit intangible | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | 59,835 | 49,675 |
| Accumulated Amortization | (38,807) | (33,861) |
| Net Carrying Amount | 21,028 | 15,814 |
| Customer base trust intangible | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | 1,600 | 1,600 |
| Accumulated Amortization | (547) | (387) |
| Net Carrying Amount | 1,053 | 1,213 |
| Manufactured housing servicing intangible | ||
| Finite-Lived Intangible Assets [Line Items] | ||
| Gross Carrying Amount | 1,088 | 1,088 |
| Accumulated Amortization | (743) | (526) |
| Net Carrying Amount | $ 345 | $ 562 |