v3.26.1
Electric utility segment - Schedule of Annual Decoupling Filings Summary (Details) - USD ($)
$ in Millions
 9 Months Ended
Mar. 31, 2026
Jun. 30, 2026
Regulatory Projects and Legal Obligations [Line Items]    
2026 ARA revenues $ 30.3  
Management Audit savings commitment (6.6)  
Recovery of COVID-19 related costs 2.7  
Return of Enterprise Resource Planning benefit liability (3.3)  
Net 2026 ARA revenues 23.1  
Incremental ARA revenues   $ (0.6)
Incremental PIMs (net)   1.1
Incremental MPIR/EPRM revenue adjustment   3.6
Incremental Pilot Process cost recovery   (0.9)
Net incremental amount to be collected under the RBA rate tariffs   3.2
Hawaiian Electric    
Regulatory Projects and Legal Obligations [Line Items]    
2026 ARA revenues 20.4  
Management Audit savings commitment (4.6)  
Recovery of COVID-19 related costs 1.8  
Return of Enterprise Resource Planning benefit liability 0.0  
Net 2026 ARA revenues 17.6  
Incremental ARA revenues   (0.4)
Incremental PIMs (net)   (2.5)
Incremental MPIR/EPRM revenue adjustment   0.7
Incremental Pilot Process cost recovery   (0.6)
Net incremental amount to be collected under the RBA rate tariffs   (2.8)
Hawaii Electric Light    
Regulatory Projects and Legal Obligations [Line Items]    
2026 ARA revenues 5.0  
Management Audit savings commitment (1.0)  
Recovery of COVID-19 related costs 0.4  
Return of Enterprise Resource Planning benefit liability (1.3)  
Net 2026 ARA revenues 3.1  
Incremental ARA revenues   (0.1)
Incremental PIMs (net)   2.2
Incremental MPIR/EPRM revenue adjustment   1.1
Incremental Pilot Process cost recovery   (0.2)
Net incremental amount to be collected under the RBA rate tariffs   3.0
Maui Electric    
Regulatory Projects and Legal Obligations [Line Items]    
2026 ARA revenues 4.9  
Management Audit savings commitment (1.0)  
Recovery of COVID-19 related costs 0.5  
Return of Enterprise Resource Planning benefit liability (2.0)  
Net 2026 ARA revenues $ 2.4  
Incremental ARA revenues   (0.1)
Incremental PIMs (net)   1.4
Incremental MPIR/EPRM revenue adjustment   1.8
Incremental Pilot Process cost recovery   (0.1)
Net incremental amount to be collected under the RBA rate tariffs   $ 3.0