Electric utility segment - Cumulative Preferred Stock (Details)	Dec. 31, 2016 $ / shares
HECO \| Series C, D, E, H, J and K Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	$ 20
Redemption price	21
HECO \| Series I Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	20
Redemption price	20
Hawaii Electric Light Company, Inc. (HELCO) \| Series G Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	100
Redemption price	100
MECO \| Series H Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	100
Redemption price	$ 100

The price per share at which the preferred stock of an entity that has priority over common stock in the distribution of dividends and in the event of liquidation of the entity is redeemed or may be called at. The redemption features of this preferred stock are solely within the control of the issuer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant