Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	$ 673,185	$ 646,055	$ 1,897,028	$ 1,763,259
Total reclassifications	346	157	1,457	464
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	598,769	572,253	1,674,255	1,549,700
Total reclassifications	22	(170)	521	(166)
Bank
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	74,289	73,708	222,474	213,297
Electric utility
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	598,769	572,253	1,674,255	1,549,700
Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	3,942	3,641	11,793	10,877
Amortization of prior service credit and net losses recognized during the period in net periodic benefit cost | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	3,618	3,314	10,857	9,941
Impact of D&Os of the PUC included in regulatory assets
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	(3,596)	(3,311)	(10,790)	(9,934)
Impact of D&Os of the PUC included in regulatory assets | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	(3,596)	(3,311)	(10,790)	(9,934)
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains (losses) on securities | Bank
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	0	0	0	360
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Forward commitments | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	0	(173)	454	(173)
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Interest rate contracts
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	0	0	0	54
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Electric utility | Forward commitments
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	$ 0	$ (173)	$ 454	$ (173)