Electric utility segment Cumulative Preferred Stock (Details)	Dec. 31, 2014 $ / shares
HECO | Multiple Series Preferred Stock
Class of Stock [Line Items]
Preferred Stock Voluntary Liquidation Preference	$ 20
Preferred Stock, Redemption Price Per Share	21
HECO | Series I Preferred Stock
Class of Stock [Line Items]
Preferred Stock Voluntary Liquidation Preference	20
Preferred Stock, Redemption Price Per Share	20
Hawaii Electric Light Company, Inc. (HELCO) | Series G Preferred Stock
Class of Stock [Line Items]
Preferred Stock Voluntary Liquidation Preference	100
Preferred Stock, Redemption Price Per Share	100
MECO | Series H Preferred Stock
Class of Stock [Line Items]
Preferred Stock Voluntary Liquidation Preference	100
Preferred Stock, Redemption Price Per Share	$ 100