Shareholders' equity - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	$ 591,562	$ 550,960
Interest expense	19,568	20,126
Total reclassifications	762	369
Electric utility
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	518,611	482,052
Hawaiian Electric Company, Inc. and Subsidiaries
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	518,611	482,052
Total reclassifications	459	14
Unrealized gains (losses) on derivatives | Interest rate contracts
Reclassifications out of accumulated other comprehensive income/(loss)
Interest expense	0	54
Unrealized gains (losses) on derivatives | Electric utility | Forward commitments
Reclassifications out of accumulated other comprehensive income/(loss)
Total revenues	454	0
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	454	0
Adjustment for 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	3,921	3,537
Adjustment for 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	3,236
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets
Reclassifications out of accumulated other comprehensive income/(loss)
Total reclassifications	3,613	3,222
Reclassification adjustment for 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	$ 3,613	$ 3,222