Electric utility subsidiary - Taxes (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Hawaiian Electric Company, Inc. and Subsidiaries
Revenue taxes
Electric Utility Revenue Taxes Included in Operating Revenues and in Taxes Other than Income Taxes Expense	$ 50	$ 64	$ 101	$ 129

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