Electric utility segment - Unconsolidated variable interest entities (Details)	3 Months Ended		9 Months Ended
	Jun. 30, 2021 MW	Mar. 31, 2021 MW	Sep. 30, 2021 agreement entity
Power purchase agreement
Number of IPPs (in entities) | entity			3
Puna Geothermal Venture Power Purchase Agreement
Power purchase agreement
Firm capacity volume (in megawatts) | MW	23.9	13
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) (in agreements) | agreement			5