Electric utility segment Cumulative Preferred Stock (Details) (USD $)	Dec. 31, 2014
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