Income taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Expense (Benefit) [Line Items]
Deferred tax assets, valuation allowance	$ 0.0	$ 0.0
Unrecognized tax benefits that would impact effective tax rate	10.2	10.2
Credit adjustments to interest expense on income taxes	0.4	0.2	$ (0.5)
Amount of accrued interest related to uncertain tax positions	0.6	0.3
Hawaiian Electric Company, Inc. and Subsidiaries
Income Tax Expense (Benefit) [Line Items]
Credit adjustments to interest expense on income taxes	0.1	0.1	$ (0.3)
Amount of accrued interest related to uncertain tax positions	$ 0.2	$ 0.1

[Line Items] for Income Tax Expense (Benefit) [Table]

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319

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- Definition

Amount of interest expense accrued for an underpayment of income taxes.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32718-109319

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- Definition

Amount of interest expense for an underpayment of income taxes.

+ References

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=SL6600010-109319

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