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Electric utility segment - Power purchase agreements (Details) - Hawaiian Electric (parent only) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 149	$ 176	$ 426	$ 472
Kalaeloa
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	39	58	111	159
AES Hawaii
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	33	38	96	102
HPOWER
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	18	20	52	57
Hamakua Energy
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	12	17	36	51
Wind IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	30	30	83	73
Solar IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	17	11	45	26
Other IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 0	$ 2	$ 3	$ 4

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Amount of operating expense for purchased power of regulated operation.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(b))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

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