Electric utility segment - Unconsolidated Variable Interest Entities (Details)	12 Months Ended
	Dec. 31, 2019 agreement entity
Variable Interest Entity [Line Items]
Number of unconsolidated VIEs	3
Hawaiian Electric Company, Inc. and Subsidiaries
Variable Interest Entity [Line Items]
Number of power purchase agreements (PPAs) | agreement	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