Electric utility segment Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Regulatory assets
Regulatory assets	$ 905,264	$ 575,924
Regulatory liabilities
Regulatory liabilities	344,849	349,299
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory assets
Regulatory assets	905,264	575,924
Regulatory liabilities
Regulatory liabilities	344,849	349,299
Hawaiian Electric Company, Inc. and Subsidiaries | Cost of removal in excess of salvage value
Regulatory liabilities
Regulatory liabilities	331,000	315,164
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans, regulatory liabilities
Regulatory liabilities
Regulatory liabilities	12,413	31,546
Authorized amortization or recovery periods	5 years
Hawaiian Electric Company, Inc. and Subsidiaries | Other, regulatory liabilities
Regulatory liabilities
Regulatory liabilities	1,436	2,589
Authorized amortization or recovery periods	5 years
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans, regulatory assets
Regulatory assets
Regulatory assets	683,243	350,821
Hawaiian Electric Company, Inc. and Subsidiaries | Income taxes, net
Regulatory assets
Regulatory assets	86,836	85,430
Hawaiian Electric Company, Inc. and Subsidiaries | Decoupling revenue balancing account
Regulatory assets
Regulatory assets	80,183	90,386
Hawaiian Electric Company, Inc. and Subsidiaries | Unamortized expense and premiums on retired debt and equity issuances
Regulatory assets
Regulatory assets	15,569	17,342
Hawaiian Electric Company, Inc. and Subsidiaries | Vacation earned, but not yet taken
Regulatory assets
Regulatory assets	10,248	9,149
Authorized amortization or recovery periods	1 year
Hawaiian Electric Company, Inc. and Subsidiaries | Postretirement benefits other than pensions
Regulatory assets
Regulatory assets	18	62
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	29,167	22,734
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 | 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 | Current assets
Regulatory assets
Regulatory assets	71,421	69,738
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term assets
Regulatory assets
Regulatory assets	833,843	506,186
Hawaiian Electric Company, Inc. and Subsidiaries | Current liabilities
Regulatory liabilities
Regulatory liabilities	632	1,916
Hawaiian Electric Company, Inc. and Subsidiaries | Long-term liabilities
Regulatory liabilities
Regulatory liabilities	$ 344,217	$ 347,383