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Share-based compensation (Details 2) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Share-based compensation    
Share-based compensation expense (in dollars) $ 1.8us-gaap_AllocatedShareBasedCompensationExpense $ 2.4us-gaap_AllocatedShareBasedCompensationExpense
Income tax benefit (in dollars) 0.6us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense 0.8us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
Hawaiian Electric Company, Inc. and Subsidiaries    
Share-based compensation    
Share-based compensation expense (in dollars) 0.5us-gaap_AllocatedShareBasedCompensationExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 0.7us-gaap_AllocatedShareBasedCompensationExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
Income tax benefit (in dollars) $ 0.2us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 $ 0.3us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember