Electric utility segment - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Regulatory assets
Regulatory assets	$ 565,543	$ 766,708
Regulatory liabilities
Regulatory liabilities	996,768	959,786
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory assets
Regulatory assets	565,543	766,708
Regulatory liabilities
Regulatory liabilities	996,768	959,786
Hawaiian Electric Company, Inc. and Subsidiaries | Cost of removal in excess of salvage value
Regulatory liabilities
Regulatory liabilities	562,514	541,730
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes
Regulatory liabilities
Regulatory liabilities	337,304	360,426
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account and RAM
Regulatory liabilities
Regulatory liabilities	251	1,957
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
Regulatory liabilities
Regulatory liabilities	51,734	29,759
Hawaiian Electric Company, Inc. and Subsidiaries | Solar tax credits
Regulatory liabilities
Regulatory liabilities	27,123	8,096
Hawaiian Electric Company, Inc. and Subsidiaries | Other
Regulatory liabilities
Regulatory liabilities	$ 17,842	17,818
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Cost of removal in excess of salvage value
Regulatory liabilities
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Income taxes
Regulatory liabilities
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Decoupling revenue balancing account and RAM
Regulatory liabilities
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Solar tax credits
Regulatory liabilities
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Other
Regulatory liabilities
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Cost of removal in excess of salvage value
Regulatory liabilities
Authorized amortization or recovery periods	79 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Income taxes
Regulatory liabilities
Authorized amortization or recovery periods	55 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Decoupling revenue balancing account and RAM
Regulatory liabilities
Authorized amortization or recovery periods	2 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Solar tax credits
Regulatory liabilities
Authorized amortization or recovery periods	20 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Other
Regulatory liabilities
Remaining amortization or recovery periods	4 years
Hawaiian Electric Company, Inc. and Subsidiaries | Current assets
Regulatory assets
Regulatory assets	$ 66,664	30,435
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term assets
Regulatory assets
Regulatory assets	498,879	736,273
Hawaiian Electric Company, Inc. and Subsidiaries | Current liabilities
Regulatory liabilities
Regulatory liabilities	29,760	37,301
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term liabilities
Regulatory liabilities
Regulatory liabilities	967,008	922,485
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans (balance primarily varies with plans’ funded statuses)
Regulatory assets
Regulatory assets	351,070	592,644
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes
Regulatory assets
Regulatory assets	$ 88,087	96,171
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes | Minimum
Regulatory assets
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes | Maximum
Regulatory assets
Authorized amortization or recovery periods	55 years
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account and RAM
Regulatory assets
Regulatory assets	$ 31,607	10,432
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account and RAM | Minimum
Regulatory assets
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account and RAM | Maximum
Regulatory assets
Authorized amortization or recovery periods	2 years
Hawaiian Electric Company, Inc. and Subsidiaries | Unamortized expense and premiums on retired debt and equity issuances
Regulatory assets
Regulatory assets	$ 7,300	8,654
Hawaiian Electric Company, Inc. and Subsidiaries | Unamortized expense and premiums on retired debt and equity issuances | Minimum
Regulatory assets
Authorized amortization or recovery periods	1 year
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Unamortized expense and premiums on retired debt and equity issuances | Maximum
Regulatory assets
Authorized amortization or recovery periods	18 years
Remaining amortization or recovery periods	18 years
Hawaiian Electric Company, Inc. and Subsidiaries | Vacation earned, but not yet taken
Regulatory assets
Regulatory assets	$ 14,255	15,665
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | COVID-19 related costs (to be determined by PUC)
Regulatory assets
Regulatory assets	$ 27,839	18,032
Hawaiian Electric Company, Inc. and Subsidiaries | Other
Regulatory assets
Regulatory assets	$ 45,385	$ 25,110
Hawaiian Electric Company, Inc. and Subsidiaries | Other | Minimum
Regulatory assets
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Other | Maximum
Regulatory assets
Remaining amortization or recovery periods	38 years