Share-based compensation - Schedule of Share-Based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Share-based compensation
Share-based compensation expense	$ 2.6	$ 2.8	$ 3.8	$ 3.5
Income tax benefit	0.5	0.5	0.6	0.5
Hawaiian Electric Company, Inc. and Subsidiaries
Share-based compensation
Share-based compensation expense	1.4	1.3	2.1	1.8
Income tax benefit	$ 0.3	$ 0.2	$ 0.4	$ 0.3

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details