Earnings per share and shareholders' equity (Details 2) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance	$ (27,378)	$ (16,750)
Current period other comprehensive income (loss)	5,361	2,756
Ending balance	(22,017)	(13,994)
Net unrealized gains (losses) on securities
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance	462	(3,663)
Current period other comprehensive income (loss)	3,608	1,691
Ending balance	4,070	(1,972)
Unrealized losses on derivatives
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance	(289)	(525)
Current period other comprehensive income (loss)	177	177
Ending balance	(112)	(348)
Retirement benefit plans
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance	(27,551)	(12,562)
Current period other comprehensive income (loss)	1,576	888
Ending balance	(25,975)	(11,674)
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning balance	45	608
Current period other comprehensive income (loss)	11	32
Ending balance	$ 56	$ 640