Dividend restrictions (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Disclosure of Restrictions on Dividends, Loans and Advances Disclosure [Abstract] | |||
| Amount available for payment of dividend without prior approval | $ 185,703,000 | $ 223,730,000 | |
| Cash dividends | 48,750,000 | $ 0 | $ 0 |
| Security dividends | $ 956,000 | ||