Credit agreement and changes in debt - Narrative (Details) - Hawaiian Electric Company, Inc. and Subsidiaries	Feb. 18, 2022 USD ($) extensionOption	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	May 14, 2021 USD ($) institution
Credit Facilities
Credit agreement
Number of financial institutions | institution				9
Credit agreement		$ 0	$ 0
HEI Facility
Credit agreement
Credit agreement				$ 175,000,000
Hawaiian Electric Facility
Credit agreement
Credit agreement	$ 275,000,000			$ 200,000,000
Number of extension options | extensionOption	2
Extension period	1 year