Mortgage servicing rights - Data and Key Economic Assumptions Related to Mortgage Servicing Rights (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Transfers and Servicing of Financial Assets [Abstract] | ||
| Unpaid principal balance | $ 9,787,657 | $ 6,734,496 |
| Weighted-average prepayment speed (CPR) | 14.07% | 10.05% |
| Estimated impact on fair value of a 10% increase | $ (4,493) | $ (2,839) |
| Estimated impact on fair value of a 20% increase | $ (8,599) | $ (5,474) |
| Discount rate | 11.49% | 9.68% |
| Estimated impact on fair value of a 100 bp increase | $ (2,942) | $ (3,086) |
| Estimated impact on fair value of a 200 bp increase | $ (5,674) | $ (5,932) |
| Weighted-average coupon interest rate | 3.58% | 4.20% |
| Weighted-average servicing fee (basis points) | 0.28% | 0.29% |
| Weighted-average remaining maturity (in months) | 328 months | 335 months |