Electric utility segment - Power purchase agreements (Details) $ in Thousands			1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2022 MWh MW	Aug. 23, 2021	Oct. 31, 2021	Jul. 31, 2018 MW	Feb. 28, 2018 USD ($) agreement MW	May 31, 2012 MW	Mar. 31, 1988 MW	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 1988 MW	Dec. 31, 2021 USD ($)
Regulatory Projects and Legal Obligations [Line Items]
Finance lease liabilities								$ 49,202		$ 49,202			$ 0
Kalaeloa
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, extension period			10 years
Purchase commitment, price increase percentage								80.00%
AES Hawaii
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, period (in years)							30 years
Minimum power volume required (in megawatts) | MW							180
Stage 1 Renewable PPAs
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, period (in years)	20 years
Minimum power volume required (in megawatts) | MW					274.5
Number of power purchase agreements (PPAs) (in agreements) | agreement					8
Estimated annual cost					$ 64,700
Generates in minimum volume required (in megawatts) | MW	39
Generates in minimum volume required (in megawatts hour) | MWh	156
Finance lease liabilities								$ 48,000		48,000
Financing lease right-of-use assets								48,000		48,000
Hu Honua Bioenergy, LLC
Regulatory Projects and Legal Obligations [Line Items]
Minimum power volume required (in megawatts) | MW						21.5
Molokai New Energy Partners
Regulatory Projects and Legal Obligations [Line Items]
Total contracted PV capacity (in megawatts) | MW				4.88
Total contracted battery energy storage system capacity | MW				3
Maximum power volume to be delivered (in megawatts) | MW				2.64
Sause Bros., Inc.
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, period (in years)		5 years
Hawaiian Electric
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								225,000	$ 186,000	607,000	$ 491,000
Hawaiian Electric | Kalaeloa
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								101,000	56,000	244,000	142,000
Increased power purchase commitment capacity (in megawatts) | MW												208
Hawaiian Electric | AES Hawaii
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								21,000	32,000	82,000	98,000
Hawaiian Electric | HPOWER
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								18,000	20,000	56,000	51,000
Hawaiian Electric | Hamakua Energy
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								16,000	15,000	46,000	38,000
Hawaiian Electric | Puna Geothermal Venture
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								13,000	9,000	37,000	20,000
Hawaiian Electric | Wind IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								37,000	38,000	93,000	95,000
Hawaiian Electric | Solar IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								18,000	12,000	44,000	40,000
Hawaiian Electric | Other IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power								$ 1,000	$ 4,000	$ 5,000	$ 7,000