Credit agreements, long-term debt and changes in long-term debt - Narrative (Details)				3 Months Ended	9 Months Ended
	Sep. 18, 2025 USD ($)	Apr. 09, 2025 USD ($)	May 17, 2024 USD ($) extensionOption	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 05, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 30, 2024 USD ($)	Dec. 06, 2024 USD ($)	Jun. 27, 2024 USD ($)	May 14, 2023 USD ($)
Debt Instrument [Line Items]
Short-term borrowings from non-affiliates, net					$ 0			$ 48,623,000
Repayments of short-term debt					50,000,000	$ 0
Aggregate principal amount, redeemed					694,475,000	12,865,000
Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Repayments of short-term debt				$ 0	50,000,000
Aggregate principal amount, redeemed					166,000,000	$ 0
Term Loan | Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Short-term borrowings from non-affiliates, net									$ 50,000,000
Debt instrument, face amount									$ 50,000,000
Stated interest rate (as percent)									7.50%
Repayments of short-term debt					50,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit agreement					844,000,000			664,000,000
Revolving Credit Facility | Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Credit agreement					619,000,000			564,000,000
HEI Facility
Debt Instrument [Line Items]
Credit agreement							$ 300,000,000					$ 175,000,000
HEI Facility | Letter of Credit
Debt Instrument [Line Items]
Credit agreement							25,000,000
HEI Facility | Bridge Loan
Debt Instrument [Line Items]
Credit agreement							30,000,000
Hawaiian Electric Facility
Debt Instrument [Line Items]
Credit agreement							300,000,000					$ 200,000,000
Accordion feature, increase limit							75,000,000
Hawaiian Electric Facility | Letter of Credit | Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Credit agreement										$ 75,000,000
Hawaiian Electric Facility | Letter of Credit
Debt Instrument [Line Items]
Credit agreement							40,000,000
Hawaiian Electric Facility | Bridge Loan
Debt Instrument [Line Items]
Credit agreement							$ 30,000,000
ABL Credit Facility Agreement | Revolving Credit Facility | Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Credit agreement					$ 244,000,000			$ 239,000,000
ABL Credit Facility Agreement | Revolving Credit Facility | Hawaiian Electric Company, Inc. and Subsidiaries | Line of credit facility
Debt Instrument [Line Items]
Credit agreement			$ 250,000,000
Credit facility period (in days)			364 days
Automatic extension expiration period (in years)			3 years
Number of extension options | extensionOption			3
Extension period			1 year
Short-term borrowings from non-affiliates, net											$ 250,000,000
HEI Private Placement
Debt Instrument [Line Items]
Aggregate principal amount, redeemed		$ 384,000,000
Interest accrued		$ 5,000,000
Senior Unsecured Notes | Hawaiian Electric Company, Inc. and Subsidiaries | Senior Notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500,000,000
Stated interest rate (as percent)	6.00%
Term	3 years