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Electric utility segment - Related-Party Transactions (Details) - Hawaiian Electric Industries, Inc. - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Hamakua Energy Partners, L.P. (HEP)
Related Party Transaction [Line Items]
Amount charged to subsidiaries for general management and administrative services	$ 3.0
Hawaiian Electric Company, Inc (HECO)
Related Party Transaction [Line Items]
Amount charged to subsidiaries for general management and administrative services		$ 6.2	$ 6.5	$ 6.5
Effective interest rate basis term		30 days
Line of credit facility basis point spread		0.15%

X

- Definition

Represents the term of commercial paper, the average effective interest rate of which is used as a basis for calculating the interest rate of the debt instrument.

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Amount of transactions with related party during the financial reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Details

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- Details

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- Details

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