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Electric utility segment - Cumulative Preferred Stock (Details) | Dec. 31, 2017 $ / shares
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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
Hawaii Electric Light Company, Inc. (HELCO) | Series G Preferred Stock |
Class of Stock [Line Items] |
Voluntary liquidation price | 100
Redemption price | 100
Maui Electric Company, Limited (MECO) | Series H Preferred Stock |
Class of Stock [Line Items] |
Voluntary liquidation price | 100
Redemption price | $ 100

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