Shareholders' equity - Accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			$ 1,927,640	$ 1,790,573
Current period other comprehensive income	$ 2,108	$ (3,127)	10,908	931
Ending Balance	1,966,182	1,898,520	1,966,182	1,898,520
AOCI Attributable to Parent [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			(26,262)	(27,378)
Current period other comprehensive income			10,908	931
Ending Balance	(15,354)	(26,447)	(15,354)	(26,447)
Net unrealized gains (losses) on securities
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			(1,872)	462
Current period other comprehensive income			9,984	(243)
Ending Balance	8,112	219	8,112	219
Unrealized gains (losses) on derivatives
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			(54)	(289)
Current period other comprehensive income			311	118
Ending Balance	257	(171)	257	(171)
Retirement benefit plans
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			(24,336)	(27,551)
Current period other comprehensive income			613	1,056
Ending Balance	(23,723)	(26,495)	(23,723)	(26,495)
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			1,728,325	1,682,144
Current period other comprehensive income	(755)	(15)	261	7
Ending Balance	1,743,006	1,696,658	1,743,006	1,696,658
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI Attributable to Parent [Member]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			925	45
Current period other comprehensive income			261	7
Ending Balance	1,186	52	1,186	52
Hawaiian Electric Company, Inc. and Subsidiaries | Unrealized gains (losses) on derivatives
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			0	0
Current period other comprehensive income			257	0
Ending Balance	257	0	257	0
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Beginning Balance			925	45
Current period other comprehensive income			4	7
Ending Balance	$ 939	$ 52	$ 939	$ 52