Electric utility segment - Related-Party Transactions (Details) - Hawaiian Electric Industries, Inc. - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Interest expense, related party	$ 40,000	$ 0	$ 0
HECO
Related Party Transaction [Line Items]
Amount charged to subsidiaries for general management and administrative services	6,500,000	6,500,000	$ 7,000,000
Due to related parties	$ 0	$ 0
Effective interest rate basis term	30 days
Line of credit facility basis point spread (as a percent)	0.15%