Long-term debt - Narrative (Details) - USD ($)			1 Months Ended	12 Months Ended
	Sep. 18, 2025	Apr. 09, 2025	Mar. 31, 2024	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Long-term debt payments, year one				$ 125,000,000
Long-term debt payments, year two				100,000,000
Long-term debt payments, year three				139,000,000
Long-term debt payments, year four				35,000,000
Long-term debt payments, year five				189,000,000
Aggregate principal amount, redeemed				733,564,000	$ 97,698,000	$ 167,080,000
Hawaiian Electric
Debt Instrument [Line Items]
Long-term debt payments, year one				0
Long-term debt payments, year two				0
Long-term debt payments, year three				72,000,000
Long-term debt payments, year four				0
Long-term debt payments, year five				39,000,000
Aggregate principal amount, redeemed				402,262,000	0	50,000,000
HEI Private Placement | Hawaiian Electric
Debt Instrument [Line Items]
Aggregate principal amount, redeemed		$ 384,000,000
Interest accrued		$ 5,000,000
Mahipapa Non-Recourse Loans | Term Loan
Debt Instrument [Line Items]
Long-term debt				54,000,000
Hawaiian Electric Company, Inc. and Subsidiaries
Debt Instrument [Line Items]
Long-term debt payments, year one				125,000,000
Long-term debt payments, year two				100,000,000
Long-term debt payments, year three				68,000,000
Long-term debt payments, year four				35,000,000
Long-term debt payments, year five				150,000,000
Aggregate principal amount, redeemed				166,000,000	81,000,000	$ 100,000,000
Long-term debt				2,195,000,000	1,908,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Senior notes
Debt Instrument [Line Items]
Long-term debt				$ 1,700,000,000	$ 1,200,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Senior Unsecured Notes | Senior notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500,000,000
Stated interest rate (as percent)	6.00%
Redemption price (as percent)	100.00%
Mahipapa, LLC | Mahipapa Non-Recourse Loans
Debt Instrument [Line Items]
Deferred payments			$ 10,000,000