Bank segment (HEI only) Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Hawaiian Electric Industries, Inc. | Consolidated subsidiary | American Savings Bank (ASB) | Management and administrative services
Revenue from related party	$ 2.3	$ 2.3	$ 1.9
Hawaiian Electric Industries, Inc. | Maximum
Obligation to contribute additional capital under the Capital Maintenance Agreement	65.1
Reduction in obligation to contribute additional capital under the Capital Maintenance Agreement	28.3
American Savings Bank (ASB)
Borrowing capacity	1,200.0	1,100.0
Cash dividends paid	$ 36.0	$ 40.0