Income taxes (Details)	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Income Tax Contingency [Line Items]
Effective income tax, percent	20.00%	17.00%
Hawaiian Electric Company, Inc. and Subsidiaries
Income Tax Contingency [Line Items]
Effective income tax, percent	19.00%	19.00%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319

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Period Type:	duration