Electric utility segment - Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Hawaiian Electric Company, Inc. and Subsidiaries
Revenue taxes
Revenue taxes included in operating revenues and in taxes other than income taxes expense	$ 50	$ 44	$ 96	$ 87