Commitments and contingencies - Lease Balances (Details) - USD ($) $ in Millions |
Jun. 30, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Commitments and Contingencies Disclosure [Abstract] | ||
| Operating lease right-of-use assets | $ 24.6 | $ 22.8 |
| Total lease liability | $ 28.0 | $ 24.5 |
| Weighted average lease term (years) | 4 years 10 months 24 days | 5 years 2 months 12 days |
| Weighted average discount rate | 3.20% | 3.00% |
| Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] | Other assets | Other assets |
| Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration] | Accounts Payable and Accrued Liabilities | Accounts Payable and Accrued Liabilities |