Electric utility segment - Unconsolidated Variable Interest Entities (Details)		12 Months Ended
	Sep. 15, 2020 agreement	Dec. 31, 2020 entity agreement
Variable Interest Entity [Line Items]
Number of unconsolidated VIEs		3
Subsidiaries
Variable Interest Entity [Line Items]
Number of power purchase agreements (PPAs) (in agreements) | agreement		4
Hawaiian Electric Company, Inc. and Subsidiaries
Variable Interest Entity [Line Items]
Number of power purchase agreements (PPAs) (in agreements) | agreement	8	4
Number of entities owning wind farms not required to be consolidated as VIE's		2
Minimum potential number of IPP entities consolidated into company in the future		1