Electric utility segment - Regulatory Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Regulatory assets
Regulatory assets	$ 957,451	$ 896,731
Regulatory liabilities
Regulatory liabilities	410,693	371,543
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory assets
Regulatory assets	957,451	896,731
Regulatory liabilities
Regulatory liabilities	410,693	371,543
Hawaiian Electric Company, Inc. and Subsidiaries | Cost of removal in excess of salvage value
Regulatory liabilities
Regulatory liabilities	394,072	357,825
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans, regulatory liabilities
Regulatory liabilities
Regulatory liabilities	$ 10,824	9,835
Authorized amortization or recovery periods	5 years
Hawaiian Electric Company, Inc. and Subsidiaries | Other, regulatory liabilities
Regulatory liabilities
Regulatory liabilities	$ 5,797	3,883
Authorized amortization or recovery periods	5 years
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans, regulatory assets
Regulatory assets
Regulatory assets	$ 745,367	679,766
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes, net
Regulatory assets
Regulatory assets	90,100	88,039
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account
Regulatory assets
Regulatory assets	73,485	74,462
Hawaiian Electric Company, Inc. and Subsidiaries | Unamortized expense and premiums on retired debt and equity issuances
Regulatory assets
Regulatory assets	12,299	14,089
Hawaiian Electric Company, Inc. and Subsidiaries | Vacation earned, but not yet taken
Regulatory assets
Regulatory assets	$ 10,970	10,420
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Postretirement benefits other than pensions
Regulatory assets
Authorized amortization or recovery periods	18 years
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Other, regulatory assets
Regulatory assets
Regulatory assets	$ 25,230	29,955
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Cost of removal in excess of salvage value
Regulatory liabilities
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Other, regulatory liabilities
Regulatory liabilities
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Income taxes, net
Regulatory assets
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Decoupling revenue balancing account
Regulatory assets
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Unamortized expense and premiums on retired debt and equity issuances
Regulatory assets
Authorized amortization or recovery periods	19 years
Remaining amortization or recovery periods	6 years
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum | Other, regulatory assets
Regulatory assets
Authorized amortization or recovery periods	1 year
Remaining amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Cost of removal in excess of salvage value
Regulatory liabilities
Authorized amortization or recovery periods	60 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Other, regulatory liabilities
Regulatory liabilities
Remaining amortization or recovery periods	2 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Income taxes, net
Regulatory assets
Authorized amortization or recovery periods	55 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Decoupling revenue balancing account
Regulatory assets
Authorized amortization or recovery periods	2 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Unamortized expense and premiums on retired debt and equity issuances
Regulatory assets
Authorized amortization or recovery periods	30 years
Remaining amortization or recovery periods	18 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum | Other, regulatory assets
Regulatory assets
Authorized amortization or recovery periods	50 years
Remaining amortization or recovery periods	46 years
Hawaiian Electric Company, Inc. and Subsidiaries | Current assets
Regulatory assets
Regulatory assets	$ 66,032	72,231
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term assets
Regulatory assets
Regulatory assets	891,419	824,500
Hawaiian Electric Company, Inc. and Subsidiaries | Current liabilities
Regulatory liabilities
Regulatory liabilities	3,762	2,204
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term liabilities
Regulatory liabilities
Regulatory liabilities	$ 406,931	$ 369,339