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Electric utility segment Consolidating Balance Sheet (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2007
Utility property, plant and equipment          
Property, plant and equipment, net $ 4,148,774us-gaap_PropertyPlantAndEquipmentNet $ 3,865,514us-gaap_PropertyPlantAndEquipmentNet      
Other long-term assets          
Total assets 11,184,161us-gaap_Assets 10,340,044us-gaap_Assets      
Capitalization          
Common stock equity 1,791,428us-gaap_StockholdersEquity 1,727,070us-gaap_StockholdersEquity 1,593,865us-gaap_StockholdersEquity 1,528,706us-gaap_StockholdersEquity  
Cumulative preferred stock-not subject to mandatory redemption 0us-gaap_PreferredStockValue 0us-gaap_PreferredStockValue      
Current liabilities          
Interest and dividends payable 25,336he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries 26,716he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries      
Deferred credits and other liabilities          
Deferred income taxes 631,734us-gaap_DeferredTaxLiabilitiesNoncurrent 529,260us-gaap_DeferredTaxLiabilitiesNoncurrent      
Contributions in aid of construction 466,432us-gaap_ContributionsInAidOfConstruction 432,894us-gaap_ContributionsInAidOfConstruction      
Total liabilities and shareholders' equity 11,184,161us-gaap_LiabilitiesAndStockholdersEquity 10,340,044us-gaap_LiabilitiesAndStockholdersEquity      
HECO          
Utility property, plant and equipment          
Land 43,819us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
43,407us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Plant and equipment 3,782,438he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
3,558,569he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Less accumulated depreciation (1,253,866)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
(1,222,129)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Construction in progress 134,376us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
124,494us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Utility property, plant and equipment, net 2,706,767us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
2,504,341us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Nonutility property, plant and equipment, less accumulated depreciation 4,950us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
4,953us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Property, plant and equipment, net 2,711,717us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
2,509,294us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Investment in wholly-owned subsidiaries, at equity 538,639us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
523,674us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Current assets          
Cash and cash equivalents 12,416us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
61,245us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
8,265us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
44,819us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
 
Advances to affiliates 16,100us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
6,839us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Customer accounts receivable, net 111,462us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
121,282us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Accrued unbilled revenues, net 103,072us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
107,752us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Other accounts receivable, net 9,980us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
16,373us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Fuel oil stock, at average cost 74,515us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
99,613us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Materials and supplies, at average cost 33,154us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
37,377us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Prepayments and other 44,680us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
29,798us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Regulatory assets 58,550us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
54,979us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total current assets 463,929us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
535,258us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Other long-term assets          
Regulatory assets 623,784us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
381,346us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Unamortized debt expense 5,640us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
6,051us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Other 53,106us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
42,163us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total other long-term assets 682,530he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
429,560he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total assets 4,396,815us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
3,997,786us-gaap_Assets
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Capitalization          
Common stock equity 1,682,144us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
1,593,564us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
1,472,136us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
1,402,841us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
 
Cumulative preferred stock-not subject to mandatory redemption 22,293us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
22,293us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Long-term debt, net 830,546us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
830,547us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total capitalization 2,534,983us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
2,446,404us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Current liabilities          
Current portion of long-term debt 0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
       
Short-term borrowings-affiliate 0us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
1,000us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Accounts payable 122,433us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
145,062us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Interest and dividends payable 15,407he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
15,190he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Taxes accrued 176,339us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
175,790us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Regulatory liabilities 191us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
1,705us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Other 48,282us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
48,443us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total current liabilities 362,652us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
387,190us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Deferred credits and other liabilities          
Deferred income taxes 429,515us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
359,621us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Regulatory liabilities 236,727us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
235,786us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Unamortized tax credits 49,865us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
44,931us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Defined benefit pension and other postretirement benefit plans liability 446,888us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
202,396us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Other 52,446us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
63,374us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total deferred credits and other liabilities 1,215,441us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
906,108us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Contributions in aid of construction 283,739us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
258,084us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Total liabilities and shareholders' equity 4,396,815us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
3,997,786us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Consolidating adjustments          
Utility property, plant and equipment          
Nonutility property, plant and equipment, less accumulated depreciation 0us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
       
Investment in wholly-owned subsidiaries, at equity (538,639)us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(523,674)us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Current assets          
Advances to affiliates (16,100)us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(7,839)us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Other accounts receivable, net (8,924)us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(9,027)us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Prepayments and other (475)us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(1,415)us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Total current assets (25,499)us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(18,281)us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Other long-term assets          
Regulatory assets (183)us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
       
Total other long-term assets (183)he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
       
Total assets (564,321)us-gaap_Assets
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(541,955)us-gaap_Assets
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Capitalization          
Common stock equity (538,639)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(523,674)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(497,939)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(516,143)us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
 
Total capitalization (538,639)us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(523,674)us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Current liabilities          
Current portion of long-term debt 0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
       
Short-term borrowings-affiliate (16,100)us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(7,839)us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Interest and dividends payable (11)he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(8)he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Taxes accrued (292)us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(1,415)us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Regulatory liabilities   0us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Other (9,096)us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(9,019)us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Total current liabilities (25,499)us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(18,281)us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Deferred credits and other liabilities          
Regulatory liabilities (183)us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
0us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
Total deferred credits and other liabilities (183)us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
       
Total liabilities and shareholders' equity (564,321)us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
(541,955)us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_ConsolidationReclassificationsAndEliminationsMember
     
HELCO          
Utility property, plant and equipment          
Land 5,464us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
5,460us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Plant and equipment 1,179,032he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
1,136,923he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Less accumulated depreciation (473,933)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
(453,721)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Construction in progress 12,421us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
7,709us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Utility property, plant and equipment, net 722,984us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
696,371us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Nonutility property, plant and equipment, less accumulated depreciation 82us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
82us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Property, plant and equipment, net 723,066us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
696,453us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Current assets          
Cash and cash equivalents 612us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
1,326us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
5,441us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
3,383us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
 
Advances to affiliates 0us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
1,000us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Customer accounts receivable, net 24,222us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
28,088us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Accrued unbilled revenues, net 15,926us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
17,100us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Other accounts receivable, net 981us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
4,265us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Fuel oil stock, at average cost 13,800us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
14,178us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Materials and supplies, at average cost 6,664us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
6,883us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Prepayments and other 8,611us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
8,334us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Regulatory assets 6,745us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
6,931us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total current assets 77,561us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
88,105us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Other long-term assets          
Regulatory assets 107,454us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
64,552us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
    12,800us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
Unamortized debt expense 1,438us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
1,580us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Other 15,366us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
11,270us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total other long-term assets 124,258he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
77,402he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total assets 924,885us-gaap_Assets
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
861,960us-gaap_Assets
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Capitalization          
Common stock equity 281,846us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
274,802us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
268,908us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
280,468us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
 
Cumulative preferred stock-not subject to mandatory redemption 7,000us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
7,000us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Long-term debt, net 190,000us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
189,998us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total capitalization 478,846us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
471,800us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Current liabilities          
Current portion of long-term debt 0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
11,400us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Short-term borrowings-affiliate 10,500us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
       
Accounts payable 23,728us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
24,383us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Interest and dividends payable 3,989he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
3,885he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Taxes accrued 37,548us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
37,899us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Regulatory liabilities   0us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Other 9,866us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
9,033us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total current liabilities 85,631us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
86,600us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Deferred credits and other liabilities          
Deferred income taxes 90,119us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
79,947us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Regulatory liabilities 77,707us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
76,475us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Unamortized tax credits 14,902us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
14,245us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Defined benefit pension and other postretirement benefit plans liability 72,547us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
28,427us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Other 10,658us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
14,703us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total deferred credits and other liabilities 265,933us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
213,797us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Contributions in aid of construction 94,475us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
89,763us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
Total liabilities and shareholders' equity 924,885us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
861,960us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
     
MECO          
Utility property, plant and equipment          
Land 3,016us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
3,016us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Plant and equipment 1,048,012he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
1,006,383he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Less accumulated depreciation (447,711)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
(435,379)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Construction in progress 11,819us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
11,030us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Utility property, plant and equipment, net 615,136us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
585,050us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Nonutility property, plant and equipment, less accumulated depreciation 1,531us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
1,532us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Property, plant and equipment, net 616,667us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
586,582us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Current assets          
Cash and cash equivalents 633us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
153us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
3,349us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
496us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
 
Advances to affiliates   0us-gaap_AdvancesToAffiliate
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Customer accounts receivable, net 22,800us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
26,078us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Accrued unbilled revenues, net 18,376us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
19,272us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Other accounts receivable, net 2,246us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
2,451us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Fuel oil stock, at average cost 17,731us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
20,296us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Materials and supplies, at average cost 17,432us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
14,784us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Prepayments and other 13,567us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
16,140us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Regulatory assets 6,126us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
7,828us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total current assets 98,911us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
107,002us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Other long-term assets          
Regulatory assets 102,788us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
60,288us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Unamortized debt expense 1,245us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
1,372us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Other 13,366us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
13,993us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total other long-term assets 117,399he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
75,653he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total assets 832,977us-gaap_Assets
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
769,237us-gaap_Assets
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Capitalization          
Common stock equity 256,692us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
248,771us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
228,927us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
235,568us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
 
Cumulative preferred stock-not subject to mandatory redemption 5,000us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
5,000us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Long-term debt, net 186,000us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
186,000us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total capitalization 447,692us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
439,771us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Current liabilities          
Current portion of long-term debt 0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
       
Short-term borrowings-affiliate 5,600us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
6,839us-gaap_DueToAffiliateCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Accounts payable 17,773us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
20,114us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Interest and dividends payable 2,931he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
2,585he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Taxes accrued 36,807us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
37,171us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Regulatory liabilities 441us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
211us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Other 16,094us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
15,424us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total current liabilities 79,646us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
82,344us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Deferred credits and other liabilities          
Deferred income taxes 83,238us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
67,593us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Regulatory liabilities 29,966us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
35,122us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Unamortized tax credits 14,725us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
14,363us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Defined benefit pension and other postretirement benefit plans liability 75,960us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
31,339us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Other 13,532us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
13,658us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total deferred credits and other liabilities 217,421us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
162,075us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Contributions in aid of construction 88,218us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
85,047us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
Total liabilities and shareholders' equity 832,977us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
769,237us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
     
HECO Consolidated          
Utility property, plant and equipment          
Land 52,299us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
51,883us-gaap_PublicUtilitiesPropertyPlantAndEquipmentLand
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Plant and equipment 6,009,482he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
5,701,875he_PublicUtilitiesPropertyPlantAndEquipmentTransmissionDistributionGenerationAndOther
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Less accumulated depreciation (2,175,510)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
(2,111,229)us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Construction in progress 158,616us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
143,233us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Utility property, plant and equipment, net 4,044,887us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
3,785,762us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Nonutility property, plant and equipment, less accumulated depreciation 6,563us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
6,567us-gaap_PropertyPlantAndEquipmentOtherNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Property, plant and equipment, net 4,051,450us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
3,792,329us-gaap_PropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Current assets          
Cash and cash equivalents 13,762us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
62,825us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
17,159us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
48,806us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
 
Customer accounts receivable, net 158,484us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
175,448us-gaap_AccountsReceivableNetCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Accrued unbilled revenues, net 137,374us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
144,124us-gaap_UnbilledReceivablesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other accounts receivable, net 4,283us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
14,062us-gaap_AccountsAndOtherReceivablesNetCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Fuel oil stock, at average cost 106,046us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
134,087us-gaap_EnergyRelatedInventory
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Materials and supplies, at average cost 57,250us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
59,044us-gaap_InventoryRawMaterialsAndSupplies
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Prepayments and other 66,383us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
52,857us-gaap_PrepaidExpenseAndOtherAssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Regulatory assets 71,421us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
69,738us-gaap_RegulatoryAssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total current assets 615,003us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
712,185us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other long-term assets          
Regulatory assets 833,843us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
506,186us-gaap_RegulatoryAssetsNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Unamortized debt expense 8,323us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
9,003us-gaap_UnamortizedDebtIssuanceExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other 81,838us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
67,426us-gaap_OtherAssetsNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total other long-term assets 924,004he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
582,615he_AssetsNoncurrentExcludingPropertyPlantAndEquipmentNet
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total assets 5,590,457us-gaap_Assets
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
5,087,129us-gaap_Assets
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Capitalization          
Common stock equity 1,682,144us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,593,564us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,472,136us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,402,841us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
 
Cumulative preferred stock-not subject to mandatory redemption 34,293us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
34,293us-gaap_PreferredStockValue
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Long-term debt, net 1,206,546us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,206,545us-gaap_LongTermDebtNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total capitalization 2,922,983us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
2,834,402us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Current liabilities          
Current portion of long-term debt 0us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
11,400us-gaap_LongTermDebtCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Accounts payable 163,934us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
189,559us-gaap_AccountsPayableCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Interest and dividends payable 22,316he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
21,652he_InterestAndDividendsPayableIncludingDividendsOnPreferredStockOfSubsidiaries
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Taxes accrued 250,402us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
249,445us-gaap_TaxesPayableCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Regulatory liabilities 632us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,916us-gaap_RegulatoryLiabilityCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other 65,146us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
63,881us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total current liabilities 502,430us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
537,853us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Deferred credits and other liabilities          
Deferred income taxes 602,872us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
507,161us-gaap_DeferredTaxLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Regulatory liabilities 344,217us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
347,383us-gaap_RegulatoryLiabilityNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Unamortized tax credits 79,492us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
73,539us-gaap_AccumulatedDeferredInvestmentTaxCredit
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Defined benefit pension and other postretirement benefit plans liability 595,395us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
262,162us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other 76,636us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
91,735us-gaap_OtherLiabilitiesNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total deferred credits and other liabilities 1,698,612us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
1,281,980us-gaap_LiabilitiesOtherThanLongtermDebtNoncurrent
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Contributions in aid of construction 466,432us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
432,894us-gaap_ContributionsInAidOfConstruction
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Total liabilities and shareholders' equity 5,590,457us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
5,087,129us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
     
Other subsidiaries          
Current assets          
Cash and cash equivalents 101us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
101us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
104us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
108us-gaap_CashAndCashEquivalentsAtCarryingValue
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
 
Total current assets 101us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
101us-gaap_AssetsCurrent
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
     
Other long-term assets          
Total assets 101us-gaap_Assets
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
101us-gaap_Assets
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
     
Capitalization          
Common stock equity 101us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
101us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
104us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
107us-gaap_StockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
 
Total capitalization 101us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
101us-gaap_CapitalizationLongtermDebtAndEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
     
Current liabilities          
Other   0us-gaap_OtherLiabilitiesCurrent
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
     
Total current liabilities   0us-gaap_LiabilitiesCurrent
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
     
Deferred credits and other liabilities          
Total liabilities and shareholders' equity $ 101us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember
$ 101us-gaap_LiabilitiesAndStockholdersEquity
/ dei_LegalEntityAxis
= he_RenewableHawaiiCompanyMember