Income taxes - Narrative (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
Dec. 06, 2023 |
|---|---|---|---|
| Operating Loss Carryforwards [Line Items] | |||
| Valuation allowance | $ 28.2 | $ 28.5 | |
| Subsidiaries | |||
| Operating Loss Carryforwards [Line Items] | |||
| Deferred tax assets | 28.2 | 28.5 | |
| Capital Loss Carryforward | |||
| Operating Loss Carryforwards [Line Items] | |||
| Tax credit carryforward | 64.0 | 63.9 | |
| Capital Loss Carryforward | Tax Year 2020 | |||
| Operating Loss Carryforwards [Line Items] | |||
| Tax credit carryforward | 225.7 | ||
| WMC | |||
| Operating Loss Carryforwards [Line Items] | |||
| Operating loss carryforwards | 317.3 | 317.3 | $ 321.6 |
| Operating loss carryforwards, not subject to expiration | $ 223.8 | ||
| WMC | Capital Loss Carryforward | |||
| Operating Loss Carryforwards [Line Items] | |||
| Tax credit carryforward | $ 154.3 | $ 153.9 |