XML 144 R120.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Income taxes - Additional Information (Details) - USD ($) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Income Tax Expense (Benefit) [Line Items] |  |  |  |
Deferred tax assets, valuation allowance | $ 0 | $ 0 | $ 0 |
Unrecognized tax benefits that would impact effective tax rate | 500,000 | 500,000 | 500,000 |
Credit adjustments to interest expense on income taxes |  | (100,000) | 200,000 | $ 200,000
Amount of accrued interest related to uncertain tax positions | 500,000 | 400,000 | 500,000 |
Decrease in net deferred tax liability |  | 13,900,000 | 271,500,000 |
Net tax expense due to impact of the Tax Act | 14,200,000 |  | 13,400,000 |
Tax Act, Increase in regulatory liabilities |  | 11,300,000 | $ 284,900,000 |
Effect of remeasurement of deferred tax assets and liabilities |  | $ 5,500,000 |  |
Effective income tax rate before adjustments |  | 22.10% |  |
Effective income tax rate |  | 20.00% | 39.60% | 33.10%
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |
Income Tax Expense (Benefit) [Line Items] |  |  |  |
Credit adjustments to interest expense on income taxes |  | $ 100,000 | $ 100,000 | $ 30,000
Amount of accrued interest related to uncertain tax positions | 200,000 | 300,000 | 200,000 |
Decrease in net deferred tax liability |  | 13,600,000 | 275,700,000 |
Net tax expense due to impact of the Tax Act | $ 9,200,000 |  | $ 9,200,000 |
Effect of remeasurement of deferred tax assets and liabilities |  | $ 5,200,000 |  |
Effective income tax rate before adjustments |  | 22.20% |  |
Effective income tax rate |  | 19.30% | 40.60% | 37.00%

X
- Definition Effective Income Tax Rate Reconciliation, Percent Before Tax Rate Adjustments + References No definition available. + Details
Name: | he_EffectiveIncomeTaxRateReconciliationPercentBeforeTaxRateAdjustments
Namespace Prefix: | he_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition [Line Items] for Income Tax Expense (Benefit) [Table] + References No definition available. + Details
Name: | he_IncomeTaxExpenseBenefitLineItems
Namespace Prefix: | he_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of reasonable estimate for income tax (expense) benefit for remeasurement of deferred tax liability from change in tax rate pursuant to Tax Cuts and Jobs Act of 2017 for which accounting for tax effect is incomplete. + References No definition available. + Details
Name: | he_TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateDeferredTaxLiabilityProvisionalIncomeTaxExpenseBenefit
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Increase In Regulatory Liabilities + References No definition available. + Details
Name: | he_TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateIncreaseInRegulatoryLiabilities
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) + References No definition available. + Details
Name: | he_TaxCutsAndJobsActOf2017IncompleteAccountingChangeInTaxRateProvisionalIncomeTaxExpenseBenefit
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
Name: | us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(2)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318 + Details
Name: | us-gaap_IncomeTaxReconciliationChangeInDeferredTaxAssetsValuationAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of interest expense accrued for an underpayment of income taxes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of interest expense for an underpayment of income taxes. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | dei_LegalEntityAxis=he_HawaiianElectricCompanyAndSubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |