Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	$ 632,281	$ 566,244	$ 1,223,843	$ 1,117,204
Interest expense	20,440	17,301	40,008	37,427
Total reclassifications	349	(63)	1,111	307
Electric utility
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	556,875	495,395	1,075,486	977,447
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	556,875	495,395	1,075,486	977,447
Total reclassifications	40	(10)	499	4
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	3,930	3,698	7,851	7,236
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	3,621	3,391	7,239	6,627
Impact of D&Os of the PUC included in regulatory assets
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	3,581	3,401	7,194	6,623
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	3,581	3,401	7,194	6,623
Reclassification out of Accumulated Other Comprehensive Income | Net unrealized gains (losses) on securities
Reclassifications out of accumulated other comprehensive income/(loss)
Revenues-bank (net gains on sales of securities)	0	360	0	360
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Interest rate contracts
Reclassifications out of accumulated other comprehensive income/(loss)
Interest expense	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 revenues	0	0	454	0
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) on derivatives | Hawaiian Electric Company, Inc. and Subsidiaries | Electric utility | Forward commitments
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	$ 0	$ 0	$ 454	$ 0