Net realized and unrealized gains - Schedule of Net Investment Gains and Losses (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Investments, Debt and Equity Securities [Abstract] | ||||
| Net investment gains recognized on equity securities during the period | $ 3,412 | $ 2,399 | $ 6,757 | $ 5,253 |
| Less: Net realized gains (losses) on equity securities sold during the period | 288 | 0 | 287 | (321) |
| Net unrealized investment gains recognized on equity securities still held | $ 3,124 | $ 2,399 | $ 6,470 | $ 5,574 |