Electric utility segment - Cumulative Preferred Stock (Details)	Dec. 31, 2018 $ / shares
Series G Preferred Stock \| Hawaii Electric Light Company, Inc. (HELCO)
Class of Stock [Line Items]
Voluntary liquidation price	$ 100
Redemption price	100
Series H Preferred Stock \| Maui Electric Company, Limited (MECO)
Class of Stock [Line Items]
Voluntary liquidation price	100
Redemption price	100
Hawaiian Electric Company, Inc (HECO) \| Series C, D, E, H, J and K Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	20
Redemption price	21
Hawaiian Electric Company, Inc (HECO) \| Series I Preferred Stock
Class of Stock [Line Items]
Voluntary liquidation price	20
Redemption price	$ 20

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21488-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21564-112644

Name:	us-gaap_PreferredStockRedemptionPricePerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant