Summary of significant accounting policies - General, Cash, and PPE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 30, 2024
Significant Accounting Policies [Line Items]
Restricted cash	$ 492,317	$ 15,028
Hawaiian Electric Company, Inc. and Subsidiaries
Significant Accounting Policies [Line Items]
Composite annual depreciation rate (as percent)	3.20%	3.20%	3.20%
Allowance for customer accounts receivable, accrued unbilled revenues and other accounts receivable	$ 5,600	$ 4,600
Weighted average AFUDC rate	7.30%	7.20%	7.10%
Minimum
Significant Accounting Policies [Line Items]
Estimated useful life under production plant (in years)	16 years
Estimated useful life under transmission and distribution plant (in years)	10 years
Estimated useful life under general plant (in years)	5 years
Maximum
Significant Accounting Policies [Line Items]
Estimated useful life under production plant (in years)	51 years
Estimated useful life under transmission and distribution plant (in years)	79 years
Estimated useful life under general plant (in years)	50 years
Hawaiian Electric Company, Inc. and Subsidiaries
Significant Accounting Policies [Line Items]
Restricted cash	$ 0	$ 2,000
GLST1, LLC
Significant Accounting Policies [Line Items]
Restricted cash held	$ 478,800
American Savings Bank (ASB) | ASB Hawaii, Inc
Significant Accounting Policies [Line Items]
Minority ownership percentage	9.90%			9.90%
Noncontrolling ownership interest	$ 44,600