Electric utility segment - HECO Capital Trust III (Details)		1 Months Ended	12 Months Ended
	May 15, 2019 USD ($)	Mar. 31, 2004 USD ($) security	Dec. 31, 2019 USD ($)
Hawaiian Electric Company, Inc. and Subsidiaries
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest income			$ 1,200,000
Hawaiian Electric Company, Inc. and Subsidiaries | 2004 Trust Preferred Securities
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Number of trust preferred securities issued (in shares) | security		2,000,000
Dividend rate on trust preferred securities		6.50%
Aggregate liquidation preference		$ 50,000,000
Securities subject o mandatory redemption, amount redeemed	$ 50,000,000
Dividend distributions on Trust Preferred Securities			1,200,000
Hawaiian Electric Company, Inc. and Subsidiaries | Trust Common Securities
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Aggregate liquidation preference		1,500,000
Securities subject o mandatory redemption, amount redeemed	$ 1,500,000
Common dividend			$ 37,000
Hawaiian Electric
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Principal amount of debentures		31,500,000
Hawaii Electric Light
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Principal amount of debentures		$ 10,000,000