Share-based compensation - Related Income Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense (in dollars)	$ 4,800	$ 6,500	$ 9,300
Income tax benefit (in dollars)	1,600	2,300	3,400
Capitalized share-based compensation expense		150	160
Hawaiian Electric Company, Inc. and Subsidiaries
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense (in dollars)	1,400	1,900	3,100
Income tax benefit (in dollars)	$ 500	$ 700	$ 1,200