Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassifications out of accumulated other comprehensive income/(loss)
Interest expense	$ 17,301	$ 18,906	$ 37,427	$ 38,006
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $2,362, $3,691, $4,619 and $7,177 for the respective periods	3,698	5,780	7,236	11,239
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,166, $3,359, $4,218 and $6,486 for the respective periods	(3,401)	(5,272)	(6,623)	(10,183)
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $2,362, $3,691, $4,619 and $7,177 for the respective periods	3,391	5,257	6,627	10,190
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,166, $3,359, $4,218 and $6,486 for the respective periods	(3,401)	(5,272)	(6,623)	(10,183)
Amount reclassified from AOCI
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	(63)	567	307	1,174
Amount reclassified from AOCI | Net unrealized gains (losses) on securities
Reclassifications out of accumulated other comprehensive income/(loss)
Net realized gains on securities	(360)	0	(360)	0
Amount reclassified from AOCI | Derivatives qualified as cash flow hedges Interest rate contracts (settled in 2011) | Interest rate contracts
Reclassifications out of accumulated other comprehensive income/(loss)
Interest expense	0	59	54	118
Amount reclassified from AOCI | Retirement benefit plans
Reclassifications out of accumulated other comprehensive income/(loss)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $2,362, $3,691, $4,619 and $7,177 for the respective periods	3,698	5,780	7,236	11,239
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,166, $3,359, $4,218 and $6,486 for the respective periods	(3,401)	(5,272)	(6,623)	(10,183)
Amount reclassified from AOCI | Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	(10)	(15)	4	7
Amount reclassified from AOCI | Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
Reclassifications out of accumulated other comprehensive income/(loss)
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $2,362, $3,691, $4,619 and $7,177 for the respective periods	3,391	5,257	6,627	10,190
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $2,166, $3,359, $4,218 and $6,486 for the respective periods	$ (3,401)	$ (5,272)	$ (6,623)	$ (10,183)