Electric utility segment - HECO Capital Trust III (Details) - VIE, Not Primary Beneficiary - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	May 15, 2019
Variable Interest Entity [Line Items]
Investment income, interest	$ 1,200	$ 2,500
Trust Preferred Securities Subject to Mandatory Redemption
Variable Interest Entity [Line Items]
Convertible preferred stock			$ 50,000
Trust Preferred Securities Subject to Mandatory Redemption | Hawaiian Electric Company
Variable Interest Entity [Line Items]
Convertible preferred stock			50,000
Distributions to holders of Trust Preferred Securities	1,200	2,400
Trust Common Securities | Hawaiian Electric Company
Variable Interest Entity [Line Items]
Convertible preferred stock			$ 1,500
Common dividends on the trust common securities	$ 37	$ 75