Share-based compensation - Share-Based Compensation Expense and Related Income Tax Benefit (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Share-based compensation
Share-based compensation expense	$ 1.3	$ 2.0
Income tax benefit	0.1	0.3
Hawaiian Electric Company, Inc. and Subsidiaries
Share-based compensation
Share-based compensation expense	0.4	0.7
Income tax benefit	$ 0.0	$ 0.1

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