Income taxes (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |
|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Income Tax Contingency [Line Items] | |||
| Effective income tax, percent | 24.00% | 27.00% | |
| Tax expense | $ 0.3 | ||
| Hawaiian Electric Company, Inc. and Subsidiaries | |||
| Income Tax Contingency [Line Items] | |||
| Effective income tax, percent | 24.00% | 21.00% | |