Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassifications out of accumulated other comprehensive income/(loss)
Revenues	$ (641,427)	$ (770,882)	$ (1,927,558)	$ (2,147,982)
Total reclassifications	603	(356)	44	54
Bank
Reclassifications out of accumulated other comprehensive income/(loss)
Revenues	(78,644)	(82,548)	(233,096)	(247,287)
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Revenues	(562,568)	(688,330)	(1,694,225)	(1,900,609)
Total reclassifications	48	26	99	73
Net realized gains on securities included in net income | Reclassification out of Accumulated Other Comprehensive Income | Bank
Reclassifications out of accumulated other comprehensive income/(loss)
Revenues	0	(478)	(1,638)	(478)
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	6,324	2,615	17,720	7,621
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	5,769	2,519	16,137	7,162
Impact of D&Os of the PUC included in regulatory assets
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	(5,721)	(2,493)	(16,038)	(7,089)
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	$ (5,721)	$ (2,493)	$ (16,038)	$ (7,089)