Electric utility subsidiary -- None. No documentation exists for this element. -- Electric utility segment Electric Utility Subsidiary [Text Block] This element encapsulates disclosures pertaining to electric utility subsidiary. Bank Segment Disclosure [Abstract] Bank Segment Disclosure [Abstract] Schedule of Assets Sold under Agreements to Repurchase [Table] Schedule of Assets Sold under Agreements to Repurchase [Table] Securities or Other Assets Sold under Agreements to Repurchase, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Assets Sold under Agreements to Repurchase, Maturity Period [Domain] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Overnight Maturity Overnight [Member] 1 to 29 days Maturity Less than 30 Days [Member] 30 to 90 days Maturity 30 to 90 Days [Member] Over 90 days Maturity Greater than 90 Days [Member] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Assets Sold under Agreements to Repurchase, Type [Domain] Assets Sold under Agreements to Repurchase, Type [Domain] Collateralized by mortgage-related securities and federal agency obligations US Government Agencies Debt Securities And Mortgage Backed Securities [Member] US Government Agencies Debt Securities And Mortgage Backed Securities [Member] Securities sold under agreements to repurchase Assets Sold under Agreements to Repurchase [Line Items] Repurchase liability Assets Sold under Agreements to Repurchase, Repurchase Liability Weighted-average interest rate Assets Sold under Agreements to Repurchase, Interest Rate Collateralized by mortgage-backed securities and federal agency obligations at fair value plus accrued interest Assets Sold Under Agreements To Repurchase Fair Value Plus Accrued Interest Assets Sold Under Agreements To Repurchase Fair Value Plus Accrued Interest Fair Value Disclosures [Abstract] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Level 3 Fair Value, Inputs, Level 3 [Member] Portfolio Segment [Axis] Class of Financing Receivable, Type [Axis] Financing Receivable Allowance [Domain] Class of Financing Receivable, Type [Domain] Home equity line of credit Home Equity Line of Credit [Member] Loans Loans [Member] Real estate acquired in settlement of loans Real Estate Acquired in Settlement of Loans [Member] Represents the portfolio segment of the entity's total financing receivables related to real estate acquired in settlement of loans financing receivables. Residential loan Residential Mortgage [Member] Commercial Commercial Loan [Member] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Fair value of property or collateral Fair Value of Property or Collateral [Member] Represents the fair value of property or collateral valuation technique used to measure fair value. Fair value of collateral Valuation, Sales Price [Member] Valuation, Sales Price [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Weighted Average Weighted Average [Member] Fair value measurements Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair value Assets, Fair Value Disclosure Selling cost Fair Value Assumptions, Selling Cost, Percent Fair Value Assumptions, Selling Cost, Percent Appraised value Fair Value Inputs Appraised Value Rate Represents the appraised value used as an input to measure fair value, expressed as a percentage. Appraised value, weighted average rate Fair Value Assumptions, Appraised Value, Weighted Average Rate Fair Value Assumptions, Appraised Value, Weighted Average Rate Statement of Comprehensive Income [Abstract] Net unrealized gains (losses) on securities arising during the period, tax (benefits) Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Reclassification adjustment for net realized gains included in net income, tax expenses Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Foreign currency hedge net unrealized loss, tax benefits Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax Unrealized interest rate hedging gain (loss), net of tax (expense) benefit Other Comprehensive Income (Loss), Interest Rate Hedge, Gain (Loss), before Reclassification, Tax Other Comprehensive Income (Loss), Interest Rate Hedge, Gain (Loss), before Reclassification, Tax Reclassification adjustment to net income, (taxes) benefits Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax Net gains (losses) arising during the period, (taxes) benefits Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax Amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, tax benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, (taxes) benefits Other Comprehensive Income, Reclassification Adjustment for Impact of Decision and Orders of the P U C Included in Regulatory Assets, Tax The amount of income taxes on the reclassification adjustments on pension and post retirement benefits for the accounting impact of the decisions issued by the Public Utilities Commission. Quarterly Financial Information Disclosure [Abstract] Schedule of Condensed Financial Statements [Table] Condensed Financial Statements [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Hawaiian Electric Company, Inc. and Subsidiaries Hawaiian Electric Company and Subsidiaries [Member] Represents Hawaiian Electric Company, Inc, and Subsidiaries. Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Revenues Revenues Operating income Operating Income (Loss) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income for common stock Net Income (Loss) Available to Common Stockholders, Basic Basic earnings per common share (in dollars per share) Earnings Per Share, Basic Diluted earnings per common share (in dollars per share) Earnings Per Share, Diluted Dividends declared per common share (in dollars per share) Common Stock, Dividends, Per Share, Declared Net tax expense due to impact of the Tax Act Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit) Deferred tax expense (benefit) tax cuts and job act of 2017, adjustment for bonuses paid Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Adjustment For Non-executive bonuses Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Adjustment For Non-executive bonuses Settlement agreement expiration, tax expense (benefit) Settlement Agreement Expiration, Revenue Adjustment, Before Taxes Settlement Agreement Expiration, Revenue Adjustment, Before Taxes Settlement agreement expiration, revenue adjustment, net of taxes Settlement Agreement Expiration, Revenue Adjustment, Net Settlement Agreement Expiration, Revenue Adjustment, Net Accounting Policies [Abstract] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Schedule of information relating to the entity's significant accounting policies. American Savings Bank (ASB) American Savings Bank FSB [Member] American Savings Bank FSB Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2016-02 Accounting Standards Update 2016-02 [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] PPAs Power Purchase Agreement [Member] Power Purchase Agreement [Member] Summary of significant accounting policies Significant Accounting Policies [Line Items] -- None. No documentation exists for this element. -- Leases Leases [Abstract] Operating lease expense Operating Leases and Rent Expense Operating lease and rent expense for each period for which an income statement is presented for minimum lease payments, contingent rentals, and sublease rentals. Future minimum lease payments Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Operating lease, liability Operating Lease, Liability Operating lease, right-of-use asset Operating Lease, Right-of-Use Asset Financial Information for Subsidiaries [Table] Financial Information for Subsidiaries [Table] Table reflecting financial information for subsidiaries of the entity. Electric utility subsidiary Financial Information for Subsidiaries [Line Items] -- None. No documentation exists for this element. -- Schedule of regulatory assets Schedule of Regulatory Assets [Table Text Block] Schedule of regulatory liabilities Schedule of Regulatory Liabilities [Table Text Block] Schedule of voluntary liquidation and redemption prices of cumulative preferred stock Schedule of Voluntary Liquidation and Redemption Prices of Cumulative Preferred Stock [Table Text Block] Tabular disclosure of the prices of cumulative preferred stock in the event of voluntary liquidation or redemption. Schedule of purchases from all IPPs Schedule of Variable Interest Entities [Table Text Block] Schedule of changes in asset retirement obligation Schedule of Change in Asset Retirement Obligation [Table Text Block] Schedule of net annual incremental amounts proposed to be collected (refunded) Schedule of Annual Decoupling Filings [Table Text Block] Schedule of Annual Decoupling Filings [Table Text Block] Schedule of consolidating statements of income Condensed Income Statement [Table Text Block] Schedule of consolidating statements of comprehensive income Schedule of Condensed Consolidating Statements of Comprehensive Income [Table Text Block] Tabular disclosure of condensed consolidating comprehensive income. Schedule of consolidating balance sheets Condensed Balance Sheet [Table Text Block] Schedule of consolidating statements of changes in common stock equity Schedule of Condensed Consolidating Statements of Changes in Common Stock Equity [Table Text Block] Tabular disclosure of changes in condensed consolidating common stock equity. Schedule of consolidating statements of cash flows Condensed Cash Flow Statement [Table Text Block] Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Cash and cash equivalents Cash, Cash Equivalents, and Federal Funds Sold Accounts receivable and unbilled revenues, net Accounts Receivable, Net Available-for-sale investment securities, at fair value Debt Securities, Available-for-sale Held-to-maturity investment securities, at amortized cost Debt Securities, Held-to-maturity Stock in Federal Home Loan Bank, at cost Federal Home Loan Bank Stock Loans held for investment, net Loans and Leases Receivable, Net Amount Loans held for sale, at lower of cost or fair value Loans Receivable Held-for-sale, Net, Not Part of Disposal Group Property, plant and equipment, net Property, Plant and Equipment, Net [Abstract] Land Land Plant and equipment Machinery and Equipment, Gross Construction in progress Construction in Progress, Gross Property, plant and equipment, gross Property, Plant and Equipment, Gross Less – accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Total property, plant and equipment, net Property, Plant and Equipment, Net Regulatory assets Regulatory Assets Other Other Assets Goodwill Goodwill Total assets Assets LIABILITIES AND SHAREHOLDERS’ EQUITY Liabilities and Equity [Abstract] Liabilities Liabilities [Abstract] Accounts payable Accounts Payable Interest and dividends payable Interest and Dividends Payable Including Dividends on Preferred Stock of Subsidiaries Sum of the carrying values as of the balance sheet date of (a) interest payable on all forms of debt, including trade payables, that has been incurred, and (b) dividends declared but unpaid on equity securities issued by the entity and outstanding (also includes dividends collected on behalf of another owner of securities that are being held by the entity). This includes dividends on preferred stock of subsidiaries. Deposit liabilities Deposits Short-term borrowings—other than bank Other Short-term Borrowings Other bank borrowings Other Bank Borrowings This element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. This item represents other bank borrowings as of the balance sheet date, including securities sold under agreements to repurchase and advances from the Federal Home Loan Bank. Long-term debt, net—other than bank Long-term Debt Deferred income taxes Deferred Income Tax Liabilities, Net Regulatory liabilities Regulatory Liabilities Defined benefit pension and other postretirement benefit plans liability Liability, Defined Benefit Plan Other Other Liabilities Total liabilities Liabilities Preferred stock of subsidiaries - not subject to mandatory redemption Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests Commitments and contingencies Commitments and Contingencies Shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, no par value, authorized 10,000,000 shares; issued: none Preferred Stock, Value, Issued Common stock, no par value, authorized 200,000,000 shares; issued and outstanding: 108,879,245 shares and 108,787,807 shares at December 31, 2018 and 2017, respectively Common Stocks, Including Additional Paid in Capital, Net of Discount Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net of tax benefits Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized losses on securities Accumulated Other Comprehensive Income (Loss), Debt Securities, Available-for-sale, Adjustment, after Tax Unrealized losses on derivatives AOCI, Derivative Qualifying as Hedge, Excluded Component, after Tax Retirement benefit plans Accumulated Other Comprehensive Income (Loss) Defined Benefit Pension and Other Postretirement Plans Net of Tax Adjusted for Regulatory Impacts The total of net (gain) loss, prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost. This amount is adjusted for regulatory rate making impacts. Accumulated other comprehensive loss, net of tax benefits Accumulated Other Comprehensive Income (Loss), Net of Tax Total shareholders’ equity Stockholders' Equity Attributable to Parent Total capitalization and liabilities Liabilities and Equity Revenue from Contract with Customer [Abstract] Disaggregation of revenue Disaggregation of Revenue [Table Text Block] Condensed Statement of Comprehensive Income [Table] Condensed Statement of Comprehensive Income [Table] Condensed Statement of Income Captions [Line Items] Condensed Statement of Income Captions [Line Items] Other comprehensive income (loss), net of taxes: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Net unrealized losses on available-for sale investment securities: Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax [Abstract] Net unrealized losses on available-for sale investment securities arising during the period, net of tax benefits of $3,468, $2,886 and $3,763 for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Reclassification adjustment for net realized gains included in net income, net of taxes of nil, nil and $238 for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Retirement benefit plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $1,108, $812 and $566 for 2018, 2017 and 2016, respectively Other Comprehensive Income, Reclassification of Defined Benefit Plans Net Gain (Loss), Prior Service Gain (Loss), and Net Transition Asset Obligation Recognized in Net Periodic Benefit Cost, Net of Tax The adjustment out of other comprehensive income for actuarial gains or losses, prior service gains or losses, and net transition asset or obligation recognized as a component of net periodic benefit cost during the period, after tax. Other comprehensive income (loss), net of taxes Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income attributable to Hawaiian Electric Company, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Weighted-average stated rate Weighted Average Rate Domestic Deposit Liabilities [Abstract] Savings Weighted Average Rate Domestic Deposit, Savings Checking, interest-bearing Weighted Average Rate Domestic Deposit, Checking Checking, Noninterest-bearing Weighted Average Rate Domestic Deposit, Checking, Noninterest-Bearing Weighted Average Rate Domestic Deposit, Checking, Noninterest-Bearing Commercial checking Weighted Average Rate Domestic Deposit, Commercial Checking Weighted Average Rate Domestic Deposit, Commercial Checking Money market Weighted Average Rate Domestic Deposit, Money Market Time certificates Weighted Average Rate Domestic Deposit, Certificates of Deposit Total weighted-average stated rate Weighted Average Rate, Interest-bearing Domestic Deposits, Point in Time Deposit liabilities Deposits [Abstract] Savings Interest-bearing Domestic Deposit, Savings Checking Deposits, Interest-bearing and Noninterest-bearing, Alternative [Abstract] Interest-bearing Interest-bearing Domestic Deposit, Checking Noninterest-bearing Noninterest-bearing Domestic Deposit, Checking Commercial checking Noninterest bearing Domestic Deposit, Commercial Checking Amount of noninterest-bearing domestic commercial checking deposit liabilities. Money market Interest-bearing Domestic Deposit, Money Market Time certificates Interest-bearing Domestic Deposit, Certificates of Deposits Total Amount Certificate accounts of $100,000 or more Time Deposits, $100,000 or More Term certificates outstanding, scheduled maturities Time Deposits, Fiscal Year Maturity [Abstract] 2019 Time Deposit Maturities, Next Twelve Months 2020 Time Deposit Maturities, Year Two 2021 Time Deposit Maturities, Year Three 2022 Time Deposit Maturities, Year Four 2023 Time Deposit Maturities, Year Five Thereafter Time Deposit Maturities, after Year Five Total Time Deposits Overdrawn deposit accounts classified as loans Overdrawn Deposit Accounts Overdrawn Deposit Accounts Interest expense on deposit liabilities by type of deposit Interest Expense, Deposits [Abstract] Time certificates Interest Expense, Time Deposits Savings Interest Expense, Savings Deposits Money market Interest Expense, Money Market Deposits Interest-bearing checking Interest Expense, Interest Bearing Checking Interest expense incurred on all interest-bearing checking. Interest expense on deposit liabilities Interest Expense, Deposits Equity [Abstract] Common stock reserved for future issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Fair Value, by Balance Sheet or Off Balance Sheet Grouping [Table] Fair Value, by Balance Sheet or Off Balance Sheet Grouping [Table] Fair value disclosures related to financial assets (as defined) and financial liabilities (as defined) whether contained in the entity's balance sheet or held off-balance sheet. Disclosures contained in this table include the carrying (reported) amount, the portion of the financial instrument (as defined) at fair value, portion at other than fair value, estimate of fair value, and the change in fair value during the period. Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying or notional amount Reported Value Measurement [Member] Estimated fair value Estimate of Fair Value Measurement [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Estimated fair value of financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Available-for-sale investment securities Held-to-maturity investment securities Debt Securities, Held-to-maturity, Fair Value Stock in Federal Home Loan Bank Investment in Federal Home Loan Bank Stock, Fair Value Disclosure Loans, net Loans Receivable, Fair Value Disclosure Mortgage servicing rights Servicing Asset at Amortized Cost Derivative assets Derivative Asset Financial liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Deposit liabilities1 Deposits, Fair Value Disclosure Long-term debt, net—other than bank Long-term Debt, Fair Value Short-term borrowings Short-term Debt, Fair Value Derivative liabilities Derivative Liability Percentage of benchmark loan to appraisal ratio in excess of which mortgage insurance is required Minimum Benchmark Percentage of Loan to Appraisal Ratio which Mortgage Insurance is Required Represents the minimum benchmark percentage of loan to appraisal ratio which mortgage insurance is required as per the policy of the reporting entity. Real estate loans for investors Real Estate Loans Serviced for Investors Real estate loans serviced for investors. Loans pledged as collateral to secure advances from the FHLB of Des Moines Loans Pledged as Collateral Loans to directors, executive directors, affiliates and any related interest of such individuals Loan Balances Related to Interest of Individual Directors Executive Officers and Related Interests Represents the amount of Loan balances, which are related to interests of individuals who are directors of bank, executive officers and related interests. Loan balances, related interests of individuals who are directors Loan Balances Related to Interest of Individual Directors Represents the amount of Loan balances, which are related to interests of individuals who are directors of bank. Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Equity Award [Domain] Common stock Common Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Shares granted Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Fair value of vested stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Income tax benefit Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Condensed Financial Information Disclosure [Abstract] Condensed Cash Flow Statement [Table] Condensed Cash Flow Statement [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Hawaiian Electric Industries, Inc. Parent Company [Member] Condensed Cash Flow Statements, Captions [Line Items] Condensed Cash Flow Statements, Captions [Line Items] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Increase in note receivable from subsidiary Repayments Of Notes Receivable To Subsidiaries Repayments Of Notes Receivable To Subsidiaries Decrease in note receivable from subsidiary Proceeds From Notes Receivable To Subsidiaries Proceeds From Notes Receivable To Subsidiaries Capital expenditures Payments to Acquire Property, Plant, and Equipment Investments in subsidiaries Payments to Acquire Interest in Subsidiaries and Affiliates Other, net Payments for (Proceeds from) Other Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Net increase (decrease) in notes payable to subsidiaries with original maturities of three months or less Proceeds from Repayments of Notes Payable to Subsidiaries Maturing in Three Months or Less Represents the cash outflow associated with notes payable to subsidiaries having initial term of payment within three months. Net increase (decrease) in short-term borrowings with original maturities of three months or less Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less Proceeds from issuance of short-term debt Proceeds from Short-term Debt Repayment of short-term debt Repayments of Short-term Debt Proceeds from issuance of long-term debt Proceeds from Issuance of Long-term Debt Repayment of long-term debt and funds transferred for redemption of special purpose revenue bonds Repayments of Long-term Debt Withheld shares for employee taxes on vested share-based compensation Payments Related to Tax Withholding for Share-based Compensation Net proceeds from issuance of common stock Proceeds from (Repurchase of) Equity Common stock dividends Payments of Ordinary Dividends, Common Stock Other Proceeds from (Payments for) Other Financing Activities Net cash used in financing activities Net Cash Provided by (Used in) Financing Activities Net decrease in cash and equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, January 1 Cash and cash equivalents, December 31 Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Premium on capital stock Additional Paid-in Capital [Member] Retained earnings Retained Earnings [Member] Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (decrease) in stockholders' equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance Balance (in shares) Common Stock, Shares, Issued Other comprehensive income (loss), net of tax benefits Reclass of AOCI for tax rate reduction impact Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings Issuance of common stock, net of expenses Stock Issued During Period, Value, New Issues Issuance of common stock, net of expenses (in shares) Stock Issued During Period, Shares, New Issues Common stock dividends Dividends, Common Stock, Cash Ending Balance Balance (in shares) Income Tax Disclosure [Abstract] Income Tax Expense (Benefit) [Table] Income Tax Expense (Benefit) [Table] Income Tax Expense (Benefit) [Table] Income Tax Expense (Benefit) [Line Items] Income Tax Expense (Benefit) [Line Items] [Line Items] for Income Tax Expense (Benefit) [Table] Federal Federal Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current Federal Tax Expense (Benefit) Deferred Deferred Federal Income Tax Expense (Benefit) Deferred tax credits, net Deferred Federal Tax Credits, Net The component of income tax expense for the period representing federal tax credits recognized during the period. Federal taxes Federal Income Tax Expense (Benefit), Continuing Operations State State and Local Income Tax Expense (Benefit), Continuing Operations [Abstract] Current Current State and Local Tax Expense (Benefit) Deferred Deferred State and Local Income Tax Expense (Benefit) Deferred tax credits, net Deferred State and Local Tax Credits, Net The component of income tax expense for the period representing state tax credits recognized during the period. State taxes State and Local Income Tax Expense (Benefit), Continuing Operations Federal and state taxes Income Tax Expense (Benefit) Net unrealized losses on available-for sale investment securities: Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent [Abstract] Derivatives qualified as cash flow hedges: Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax, Parent [Abstract] Effective portion of foreign currency hedge net unrealized losses arising during the period, net of tax benefits of nil, nil and $179 for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Unrealized interest rate hedging gain (loss), net of tax (expense) benefit of $151, nil and nil for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Interest Rate Hedge, Gain (Loss), before Reclassification, after Tax Other Comprehensive Income (Loss), Interest Rate Hedge, Gain (Loss), before Reclassification, after Tax Reclassification adjustment to net income, net of (taxes) benefits of nil, $289 and $(76) for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax Retirement benefit plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax and Reclassification Adjustment, Attributable to Parent [Abstract] Net gains (losses) arising during the period, net of (taxes) benefits of $9,810, $(41,129) and $27,703 for 2018, 2017 and 2016, respectively Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $7,317, $10,041 and $9,267 for 2018, 2017 and 2016, respectively Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(2,887), $49,523 and $(18,206) for 2018, 2017 and 2016, respectively Other Comprehensive Income, Reclassification Adjustment for Impact of Decision and Orders of the P U C Included in Regulatory Assets, Net of Tax Reclassification adjustments on pension and post retirement benefits for the accounting impact of the decisions issued by the Public Utilities Commission, net of income taxes. Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Mortgage-related securities - FNMA, FHLMC and GNMA Collateralized Mortgage Backed Securities [Member] Federal Home Loan Bank Branch [Axis] Federal Home Loan Bank Branch [Axis] Federal Home Loan Bank Branch [Domain] Federal Home Loan Bank Branch [Domain] FHLB Des Moines Federal Home Loan Bank of Des Moines [Member] Available-for-sale securities Debt Securities, Available-for-sale [Line Items] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Due in one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Due after ten years Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Amortized cost, available-for-sale securities with a single maturity date Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Mortgage-related securities-FNMA, FHLMC and GNMA - amortized cost Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Total amortized cost Debt Securities, Available-for-sale, Amortized Cost Mortgage-related securities-FNMA, FHLMC and GNMA, amortized cost basis Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost Debt Securities, Held-to-maturity Fair value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Due in one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Due after ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Available-for-sale securities with a single maturity date Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value Mortgage-related securities-FNMA, FHLMC and GNMA - fair value Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Total fair value Mortgage-related securities - FNMA, FHLMC and GNMA, Fair Value Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value Held-to-maturity securities, Fair Value Gains (losses) from sales of available-for-sale investments Debt Securities, Available-for-sale, Realized Gain (Loss) [Abstract] Proceeds Proceeds from Sale of Debt Securities, Available-for-sale Gross gains Debt Securities, Available-for-sale, Realized Gain Gross losses Debt Securities, Available-for-sale, Realized Loss Interest income from taxable and non-taxable investment securities Interest Income, Securities, Operating, by Taxable Status [Abstract] Taxable Interest Income, Securities, Operating, Taxable Non-taxable Interest Income, Securities, Operating, Tax Exempt Total Interest Income, Operating Available-for-sale securities pledged at carrying value Available for sale Securities, Pledged at Carrying Value as Collateral The carrying value of available-for-sale securities that serve as collateral for deposits and borrowings. Available-for-sale securities, pledged at carrying value as collateral for securities sold under agreements to repurchase Available-for-sale Securities, Pledged at Carrying Value as Collateral for Securities Sold under Repurchase Agreement Represents the carrying value of available-for-sale securities that serve as collateral for borrowings, sold under agreements to repurchase. Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Hamakua Energy Partners, L.P. (HEP) Hamakua Energy Partners L P [Member] Represents an independent power producer (IPP) with whom the entity has entered into a power purchase agreement. Mauo, LLC Mauo, LLC [Member] Mauo, LLC [Member] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Intersegment eliminations Intersegment Eliminations [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Electric utility Electric Utility Segment [Member] Represents information about the electric utility business segment of the company. Certain subsidiaries of the company are regulated operating public utilities engaged in the production, purchase, transmission, distribution and sale of electricity. Bank Banking Segment [Member] Represents information about the banking business segment of the company. Other Other Segments [Member] Segment financial information Segment Reporting Information [Line Items] Power produced by power plants (in megawatts) Public Utilities, Power Produced By Power Plant Public Utilities, Power Produced By Power Plant Power storage capacity (in megawatt hours) Public Utilities, Power Storage Capacity Public Utilities, Power Storage Capacity Power purchase agreement term Public Utilities, Power Purchase Agreement, Term Public Utilities, Power Purchase Agreement, Term Power purchase agreement extension term Public Utilities, Power Purchase Agreement, Term Extension Period Public Utilities, Power Purchase Agreement, Term Extension Period Number of project sites expected to be placed in service during 2019 and 2020 Public Utilities, Power Purchase Agreement, Number Of Project Sites To Be Placed Into Service In Next Two Years Public Utilities, Power Purchase Agreement, Number Of Project Sites To Be Placed Into Service In Next Two Years Revenues Revenue from Contract with Customer, Including Assessed Tax Depreciation and amortization Depreciation, Depletion and Amortization Interest expense, net Interest Expense Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income taxes (benefit) Net income (loss) Preferred stock dividends of subsidiaries Noncontrolling Interest in Net Income (Loss) Preferred Unit Holders, Redeemable Net income for common stock Capital expenditures Assets SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Electric utility subsidiary [Abstract] Electric utility subsidiary [Abstract] Hawaiian Electric Hawaiian Electric, Parent [Member] Hawaiian Electric, Parent [Member] Hawaii Electric Light Company, Inc. (HELCO) Subsidiaries Two [Member] This element represents Hawaii Electric Light Company, Inc., an electric utility subsidiary of Hawaiian Electric Company, Inc. Maui Electric Company, Limited (MECO) Subsidiaries Three [Member] This element represents Maui Electric Company, Limited, an electric utility subsidiary of Hawaiian Electric Company, Inc. Other subsidiaries Other Subsidiaries [Member] Other Subsidiaries [Member] Consolidating adjustments Consolidation Reclassifications and Eliminations [Member] Reclassifications and eliminating entries used in consolidating a parent entity and its subsidiaries. HECO Consolidated Effective portion of foreign currency hedge net unrealized gains net of taxes Reclassification adjustment to net income, net of (taxes) benefit Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits of $(2,887), $49,523 and $(18,206) for 2018, 2017 and 2016, respectively Income Tax Contingency [Table] Income Tax Contingency [Table] Income Tax Contingency [Line Items] Income Tax Contingency [Line Items] Deferred tax assets Deferred Tax Assets, Net [Abstract] Regulatory liabilities, excluding amounts attributable to property, plant and equipment Deferred Tax Assets, Regulatory Assets and Liabilities Allowance for bad debts Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Other Deferred Tax Assets, Other Total deferred tax assets Deferred Tax Assets, Gross Deferred tax liabilities Deferred Tax Liabilities, Gross [Abstract] Property, plant and equipment related Deferred Tax Liabilities, Property, Plant and Equipment Regulatory assets, excluding amounts attributable to property, plant and equipment Deferred Tax Liabilities, Regulatory Assets Deferred RAM and RBA revenues Deferred Tax Liabilities, Deferred Rate Adjustment Mechanism and RBA Revenues Deferred Tax Liabilities, Deferred Rate Adjustment Mechanism and RBA Revenues Retirement benefits Deferred Tax Liabilities Deferred Expense Postretirement Benefits The amount as of the balance sheet date of the estimated future tax effects attributable to the difference between the tax basis and the basis in accordance with generally accepted accounting principles of retirement benefits which will increase future taxable income when such basis difference reverses. Other Deferred Tax Liabilities, Other Total deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred income tax liability Deferred Tax Liabilities, Net Regulatory Capital Requirements [Abstract] Regulatory restrictions on net assets Regulatory Restrictions on Net Assets Disclosure [Text Block] Entire disclosure of regulatory agencies restrictions on net asset and limitations on transfers out of the company. Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Assets Accounts receivable Notes receivable Notes, Loans and Financing Receivable, Net, Current Property, plant and equipment, net Deferred income tax assets Deferred Income Tax Assets, Net Other assets Investments in subsidiaries, at equity Investment in Subsidiaries The entity's equity interest in its subsidiaries. Interest payable Interest Payable Notes payable to subsidiaries Notes Payable to Subsidiaries The carrying value as of the balance sheet date of notes payable to subsidiaries. Commercial paper Commercial Paper Short-term debt, net Short-term Debt Long-term debt, net Retirement benefits liability Postemployment Benefits Liability Common stock equity Accumulated other comprehensive loss Preferred stock, authorized shares Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Common stock, authorized shares Common Stock, Shares Authorized Common stock, issued shares Common stock, outstanding shares Common Stock, Shares, Outstanding Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Not Primary Beneficiary Variable Interest Entity, Not Primary Beneficiary [Member] Tax Credit Carryforward [Line Items] Tax Credit Carryforward [Line Items] Amortization recognized in the provision for income taxes Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Amount Tax credits and other tax benefits recognized in the provision for income taxes Effective Income Tax Rate Reconciliation, Tax Credits And Other Adjustments Effective Income Tax Rate Reconciliation, Tax Credits And Other Adjustments Net benefit to income tax expense Business Combinations [Abstract] Termination of proposed merger and other matters Business Combination Disclosure [Text Block] Restricted stock units Restricted Stock Units (RSUs) [Member] Share-based Compensation, Restricted Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding, beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding, end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding, beginning of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding, end of period (in dollars per share) Total weighted-average grant-date fair value Share Based Compensation Arrangement by Share Based Payment Award Equity Instruments Other than Options Grants in Period Total Fair Value Represents the total weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Derivative [Table] Derivative [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Lock Commitments Interest Rate Lock Commitments [Member] Forward commitments Forward Contracts [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Mortgage banking income Fees and Commissions, Mortgage Banking [Member] Fees and Commissions, Mortgage Banking [Member] Derivative instrument Derivative [Line Items] Notional amount Derivative, Notional Amount Fair value Derivative, Fair Value, Net Asset derivative Derivative Asset, Fair Value, Amount Not Offset Against Collateral Liability derivative Derivative Liability, Fair Value, Amount Not Offset Against Collateral Net gains (losses) recognized in the Statement of Income Derivative, Gain (Loss) on Derivative, Net Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series C, 4.25% Preferred Stock Series C 4.25 Percent Preferred Stock [Member] This element represents cumulative preferred stock not subject to mandatory redemption, C-4.25% Series. Series D, 5.00% Preferred Stock Series D 5 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, D-5% Series. Series E, 5.00% Preferred Stock Series E 5 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, E-5% Series. Series H, 5.25% Preferred Stock Series H 5.25 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, H-5 1/4% Series. Series I, 5.00% Preferred Stock Series I 5 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, l-5% Series. Series J, 4.75% Preferred Stock Series J 4.75 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, J-4 3/4% Series. Series K, 4.65% Preferred Stock Series K 4.65 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, K-4.65% Series. Series G, 7.625% Preferred Stock Series G 7.625 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, G-7 5/8% Series of subsidiaries two. Series H, 7.625% Preferred Stock Series H 7.625 Percent Preferred Stock [Member] This element represents Cumulative preferred stock not subject to mandatory redemption, H-7 5/8% Series of subsidiaries three. Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 3.10%, Refunding series 2017A, due 2026 Refunding Series 2017A Due 2026 3.10 Percent [Member] Refunding Series 2017A Due 2026 3.10 Percent [Member] 4.00%, Refunding series 2017B, due 2037 Refunding Series 2017B, Due 2037, 4.00 Percent [Member] Refunding Series 2017B, Due 2037, 4.00 Percent [Member] 3.25%, Refunding series 2015, due 2025 3.25% Refunding Series 2015 SPRBs due 2025 [Member] 3.25% Refunding Series 2015 SPRBs due 2025 [Member] 6.50%, Series 2009, due 2039 Series 2009 Due 2039 Debt 6.50 Percent [Member] This element represents Special Purpose Revenue Bonds, 6.50%, series 2009, due 2039. Senior notes Senior Notes [Member] 4.38%, Series 2018A, due 2028 Unsecured Senior Notes, At 4.38 Percent And Due 2028 [Member] Unsecured Senior Notes, At 4.38 Percent And Due 2028 [Member] 4.53%, Series 2018B, due 2033 Unsecured Senior Notes, At 4.53 Percent And Due 2033 [Member] Unsecured Senior Notes, At 4.53 Percent And Due 2033 [Member] 4.72%, Series 2018C, due 2048 Unsecured Senior Notes, At 4.72 Percent And Due 2048 [Member] Unsecured Senior Notes, At 4.72 Percent And Due 2048 [Member] 4.31%, Series 2017A, due 2047 Unsecured Senior Notes, At 4.31 Percent And Due 2047 [Member] Unsecured Senior Notes, At 4.31 Percent And Due 2047 [Member] 4.54%, Series 2016A, due 2046 Unsecured Senior Notes Due 2046, 4.54% [Member] Unsecured Senior Notes Due 2046, 4.54% [Member] 5.23%, Series 2015A, due 2045 Unsecured Senior Notes Due 2045, 5.23% [Member] Unsecured Senior Notes Due 2045, 5.23% [Member] 3.83%, Series 2013A, due 2020 Unsecured Senior Notes Due 2020, 3.83% [Member] Unsecured Senior Notes Due 2020, 3.83% [Member] 4.45%, Series 2013A and 2013B, due 2022 Unsecured Senior Notes Due 2022, 4.45% [Member] Unsecured Senior Notes Due 2022, 4.45% [Member] 4.84%, Series 2013A, 2013B and 2013C, due 2027 Unsecured Senior Notes Due July, 2027, 4.84% [Member] Unsecured Senior Notes Due July, 2027, 4.84% [Member] 5.65%, Series 2013B and 2013C, due 2043 Unsecured Senior Notes Due 2043, 5.65% [Member] Unsecured Senior Notes Due 2043, 5.65% [Member] 3.79%, Series 2012A, paid in 2018 Unsecured Senior Notes Due 2018, 3.79% [Member] Unsecured Senior Notes Due 2018, 3.79% [Member] 4.03%, Series 2012B, due 2020 Unsecured Senior Notes Due 2020, 4.03% [Member] Unsecured Senior Notes Due 2020, 4.03% [Member] 4.55%, Series 2012B and 2012C, due 2023 Unsecured Senior Notes Due 2023, 4.55% [Member] Unsecured Senior Notes Due 2023, 4.55% [Member] 4.72%, Series 2012D, due 2029 Unsecured Senior Notes Due 2029, 4.72% [Member] Unsecured Senior Notes Due 2029, 4.72% [Member] 5.39%, Series 2012E, due 2042 Unsecured Senior Notes Due 2042, 5.39% [Member] Unsecured Senior Notes Due 2042, 5.39% [Member] 4.53%, Series 2012F, due 2032 Unsecured Senior Notes 4.53 Percent Due 2032 [Member] Unsecured Senior Notes 4.53 Percent Due 2032 [Member] 6.50 %, series 2004, Junior subordinated deferrable interest debentures, due 2034 Series 2004 Junior Subordinated 6.50 Percent Deferrable Interest Debentures Series Due 2034 [Member] Represents Junior Subordinated Deferrable Interest Debentures bearing an interest rate of 6.50 percent, series 2004, due in 2034. Common stock equity Common Stock Equity [Abstract] -- None. No documentation exists for this element. -- Common stock of $6 2/3 par value, Authorized: 50,000,000 shares. Outstanding: 16,142,216 shares and 16,019,785 shares at December 31, 2017 and 2016, respectively Common Stock, Value, Issued Premium on capital stock Additional Paid in Capital Accumulated other comprehensive income (loss), net of taxes-retirement benefit plans Preferred stock, par value (in dollars per share) Temporary Equity, Par or Stated Value Per Share Shares outstanding December 31, 2018 and 2017 Temporary Equity, Shares Outstanding Obligations to the State of Hawaii for the repayment of Special Purpose Revenue Bonds (subsidiary obligations unconditionally guaranteed by Hawaiian Electric): Secured Debt [Abstract] -- None. No documentation exists for this element. -- Secured long-term debt Secured Debt Other long-term debt – unsecured: Unsecured Debt. [Abstract] -- None. No documentation exists for this element. -- Other long-term debt - unsecured Unsecured Debt Total long-term debt Long-term Debt, Gross Less unamortized debt issuance costs Debt Instrument, Unamortized Discount Less current portion long-term debt, net of unamortized debt issuance costs Long-term Debt, Current Maturities Long-term debt, net Long-term Debt, Excluding Current Maturities Total capitalization Capitalization, Long-term Debt and Equity Utility property, plant and equipment Public Utilities, Property, Plant and Equipment, Net [Abstract] Land Public Utilities, Property, Plant and Equipment, Land Plant and equipment Public Utilities Property Plant and Equipment Transmission Distribution Generation and Other Period end amount of property, plant and equipment (PPE) related to transmission, distribution, generation and other owned by public utility. Less accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Construction in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Utility property, plant and equipment, net Public Utilities, Property, Plant and Equipment, Net Nonutility property, plant and equipment, less accumulated depreciation Non-utilities, Property, Plant and Equipment, Net Non-utilities, Property, Plant and Equipment, Net Investment in wholly-owned subsidiaries, at equity Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Current assets Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Advances to affiliates Advances to Affiliate Customer accounts receivable, net Accounts Receivable, Net, Current Accrued unbilled revenues, net Unbilled Receivables, Current Other accounts receivable, net Accounts and Other Receivables, Net, Current Fuel oil stock, at average cost Energy Related Inventory Materials and supplies, at average cost Inventory, Raw Materials and Supplies, Gross Prepayments and other Prepaid Expense and Other Assets, Current Regulatory assets Regulatory Assets, Current Total current assets Assets, Current Other long-term assets Other Long-term Debt [Abstract] Regulatory assets Regulatory Assets, Noncurrent Other Other Assets, Noncurrent Total other long-term assets Assets Noncurrent Excluding Property, Plant and Equipment, Net The carrying value of assets which are intended to be held for a period exceeding one year, excluding property, plant and equipment. Capitalization and liabilities Capitalization Common stock equity Cumulative preferred stock – not subject to mandatory redemption Current liabilities Liabilities, Current [Abstract] Current portion of long-term debt Short-term borrowings from non-affiliate Short-term borrowings-affiliate Due to Affiliate, Current Accounts payable Accounts Payable, Current Taxes accrued, including revenue taxes Taxes Payable, Current Regulatory liabilities Regulatory Liability, Current Other Other Liabilities, Current Total current liabilities Liabilities, Current Deferred credits and other liabilities Liabilities, Noncurrent [Abstract] Deferred income taxes Regulatory liabilities Regulatory Liability, Noncurrent Unamortized tax credits Accumulated Deferred Investment Tax Credit Defined benefit pension and other postretirement benefit plans liability Liability, Defined Benefit Plan, Noncurrent Other Other Liabilities, Noncurrent Total deferred credits and other liabilities Liabilities, Other than Long-term Debt, Noncurrent Statement of Cash Flows [Abstract] Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation of property, plant and equipment Depreciation Other amortization Amortization Provision for loan losses Provision for Loan and Lease Losses Loans originated and purchased, held for sale Payments for Origination and Purchases of Loans Held-for-sale Proceeds from sale of loans, held for sale Proceeds from Sale of Loans Held-for-sale Deferred income taxes Deferred Income Tax Expense (Benefit) Share-based compensation expense Share-based Compensation Allowance for equity funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Other Other Operating Activities, Cash Flow Statement Changes in assets and liabilities Increase (Decrease) in Operating Capital [Abstract] Increase in accounts receivable and unbilled revenues, net Increase (Decrease) in Receivables Decrease (increase) in fuel oil stock Increase (Decrease) in Fuel Inventories Decrease (increase) in regulatory assets Increase (Decrease) in Other Regulatory Assets Increase (decrease) in accounts, interest and dividends payable Increase (Decrease) in Accounts Payable and Interest and Dividends Payable The increase (decrease) during the reporting period in accounts, interest and dividends payable. Change in prepaid and accrued income taxes, tax credits and utility revenue taxes Increase (Decrease) In Prepaid And Accrued Income Taxes, Tax Credits, And Utility Revenue, Taxes Increase (Decrease) In Prepaid And Accrued Income Taxes, Tax Credits, And Utility Revenue, Taxes Increase in defined benefit pension and other postretirement benefit plans liability Increase (Decrease) in Obligation, Pension and Other Postretirement Benefits Change in other assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Net cash provided by operating activities Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Available-for-sale investment securities purchased Payments to Acquire Debt Securities, Available-for-sale Principal repayments on available-for-sale investment securities Proceeds from Principal Repayments on Investment and Mortgage Related Securities The net cash inflow (outflow) resulting from principal repayments on investment and mortgage-related securities. Proceeds from sale of available-for-sale investment securities Purchases of held-to-maturity investment securities Payments to Acquire Held-to-maturity Securities Proceeds from repayments or maturities of held-to-maturity investment securities Proceeds from Sale and Maturity of Held-to-maturity Securities Purchase of stock from Federal Home Loan Bank Payments to Acquire Federal Home Loan Bank Stock Redemption of stock from Federal Home Loan Bank Proceeds from Sale of Federal Home Loan Bank Stock Net decrease (increase) in loans held for investment Payments for (Proceeds from) Loans and Leases Proceeds from sale of commercial loans Proceeds from Sale of Loans Receivable Proceeds from sale of real estate acquired in settlement of loans Proceeds from Sale of Wholly Owned Real Estate and Real Estate Acquired in Settlement of Loans Proceeds from sale of real estate held for sale Proceeds from Sale of Property Held-for-sale Contributions in aid of construction Proceeds from Contribution in Aid of Construction Contributions to low income housing investments Payments for Affordable Housing Programs Acquisition of business Payments to Acquire Businesses, Net of Cash Acquired Net increase in deposit liabilities Increase (Decrease) in Deposits Net increase (decrease) in retail repurchase agreements Increase (Decrease) in Retail Repurchase Agreements The decrease in retail repurchase agreements, during the period. Proceeds from other bank borrowings Proceeds from Other Bank Borrowings The amount of cash inflows resulting from other bank borrowings. Repayments of other bank borrowings Repayments of Other Bank Borrowings The amount of cash outflows resulting from repayment of other bank borrowings. Withheld shares for employee taxes on vested share-based compensation Excess Tax Benefit from Share-based Compensation, Financing Activities Net proceeds from issuance of common stock Preferred stock dividends of subsidiaries Payments of Ordinary Dividends, Noncontrolling Interest Segment financial information Segment Reporting Disclosure [Text Block] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Residential 1-4 family Residential 1 to 4 Family Portfolio Segment [Member] Portfolio segment of the company's total financing receivables related to residential 1-4 family financing receivables. Commercial real estate Commercial Real Estate Portfolio Segment [Member] Residential land Residential Land Portfolio Segment [Member] Portfolio segment of the company's total financing receivables related to residential land receivables. Commercial construction Construction Loans [Member] Residential construction Residential Construction Portfolio Segment [Member] Portfolio segment of the company's total financing receivables related to residential construction. Consumer Consumer Loan [Member] Allowance for loan losses Financing Receivable, Allowance for Credit Losses [Line Items] Allowance for loan losses: Financing Receivable, Allowance for Credit Losses [Roll Forward] Valuation allowance, balance at the beginning of the period Financing Receivable, Allowance for Credit Losses Charge-offs Financing Receivable, Allowance for Credit Losses, Write-downs Recoveries Financing Receivable, Allowance for Credit Losses, Recovery Provision Provision for Loan, Lease, and Other Losses Valuation allowance, balance at the end of the period Ending balance: individually evaluated for impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Ending balance: collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Financing Receivables: Financing Receivable, Net [Abstract] Total financing receivables Financing Receivable, Net Ending balance: individually evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Ending balance: collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Components of income taxes attributable to net income for common stock Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of reconciliation of amount of income taxes computed at federal statutory rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of changes in total unrecognized tax benefits Summary of Income Tax Contingencies [Table Text Block] Retirement Benefits [Abstract] Retirement benefits Pension and Other Postretirement Benefits Disclosure [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair value measurements on a nonrecurring basis Fair Value, Measurements, Nonrecurring [Member] Fair value measurements on a recurring and nonrecurring basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Loans Real estate acquired in settlement of loans Real Estate Acquired Through Foreclosure, Fair Value Disclosure Real Estate Acquired Through Foreclosure, Fair Value Disclosure Shareholders' equity Stockholders' Equity Note Disclosure [Text Block] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Consolidated subsidiary Consolidated Subsidiary [Member] Consolidated Subsidiary [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Management and administrative services Management and Administrative Services [Member] Management and Administrative Services [Member] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Obligation to contribute additional capital under the Capital Maintenance Agreement Obligation to Contribute Additional Capital under Capital Maintenance Agreement Represent the amount of maximum obligation to contribute additional capital under the Capital Maintenance Agreement. Reduction in obligation to contribute additional capital under the Capital Maintenance Agreement Remaining Obligation to Contribute Additional Capital under Capital Maintenance Agreement Represent the remaining amount of maximum obligation to contribute additional capital under the Capital Maintenance Agreement. Cash dividends paid SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Subsidiaries and Equity Method Investees Revenue from related party Revenue from Related Parties New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] HELCO Hawaii Electric Light Company, Inc [Member] Hawaii Electric Light Company, Inc [Member] MECO Maui Electric Company Limited [Member] Maui Electric Company Limited [Member] ASU 2017-07 Accounting Standards Update 2017-07 [Member] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] As previously filed Previously Reported [Member] Adjustment Restatement Adjustment [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Total expenses Costs and Expenses Operating income Retirement defined benefits expense—other than service costs Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Other operation and maintenance Utilities Operating Expense, Maintenance and Operations Compensation and employee benefits Labor and Related Expense Other expense Other Noninterest Expense Cash and due from banks Interest-bearing deposits Interest-bearing Deposits in Banks and Other Financial Institutions Investment securities Investments [Abstract] Available-for-sale, at fair value Held-to-maturity, at amortized cost (fair value of $142,057 and $44,412 at December 31, 2018 and 2017, respectively) Stock in Federal Home Loan Bank, at cost Loans held for investment Loans and Leases Receivable, Net of Deferred Income Allowance for loan losses Loans and Leases Receivable, Allowance Total loans, net Deposit liabilities–noninterest-bearing Noninterest-bearing Deposit Liabilities Deposit liabilities–interest-bearing Interest-bearing Deposit Liabilities Other borrowings Other Borrowings Commitments and contingencies Common stock Additional paid in capital Additional Paid in Capital, Common Stock Retirement benefit plans Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Other assets Other Assets [Abstract] Bank-owned life insurance Bank Owned Life Insurance Premises and equipment, net Accrued interest receivable Interest Receivable Low-income housing investments Affordable Housing Program Equity Investment Affordable Housing Program Equity Investment Real estate acquired in settlement of loans, net Real Estate Acquired Through Foreclosure Other Other Assets, Miscellaneous Total other assets Other liabilities Other Liabilities [Abstract] Accrued expenses Accrued Liabilities Federal and state income taxes payable Accrued Income Taxes Cashier’s checks Cashier Checks Cashier's check is a check drawn directly on a customer's account, making the bank the primary obligor, and assuring firm that the amount will be paid. Advance payments by borrowers Advance Payments by Borrowers for Taxes and Insurance Other Other Sundry Liabilities Total other liabilities Document and Entity Information -- None. No documentation exists for this element. -- Entities [Table] Entities [Table] Entity Information [Line Items] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Regulatory Projects and Legal Obligations [Table] Regulatory Projects and Legal Obligations [Table] Discloses the components of regulatory projects and legal obligations. Island Energy Services, LLC (IES) Island Energy Services, LLC [Member] Island Energy Services, LLC [Member] AES Hawaii, Inc. (AES Hawaii) AES Hawaiian Inc [Member] Represents an independent power producer (IPP) with whom the entity has entered into a power purchase agreement. Hu Honua Bioenergy Hu Honua Bioenergy, LLC [Member] Hu Honua Bioenergy, LLC [Member] Kalaeloa Partners, L.P. (Kalaeloa) Kalaeloa Partners L P [Member] Represents an independent power producer (IPP) with whom the entity has entered into a power purchase agreement. Hawaiian Telcom Hawaiian Telcom [Member] Hawaiian Telcom [Member] PGV Facility PGV Facility [Member] PGV Facility [Member] Hawaiian Electric Company, Inc (HECO) Subsidiaries [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Major Vendor [Axis] Major Vendor [Axis] Vendor that is considered major by the entity. Major Vendor [Domain] Major Vendor [Domain] Name and description of the vendor that account for major purchases of the entity. Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Axis] Environmental Remediation Contingency [Domain] Environmental Remediation Contingency [Domain] PCB Contamination PCB Contamination [Member] PCB Contamination [Member] Regulatory Projects and Legal Obligations [Line Items] Regulatory Projects and Legal Obligations [Line Items] -- None. No documentation exists for this element. -- Fuel contracts Fuel Supply Contracts [Abstract] -- None. No documentation exists for this element. -- Period prior to year end for written notice for cancellation Public Utility, Fuel Contract, Period Prior To Year End For Written Notice Of Cancellation Public Utility, Fuel Contract, Period Prior To Year End For Written Notice Of Cancellation Estimated cost of minimum purchase within 2018 year Long Term Purchase Commitment Amount within One Year The minimum estimated amount in the first year after the balance sheet date the entity agreed to spend under the long-term purchase commitment. Cost of purchases Cost of Purchases Represents the actual cost of purchases. Revenue subject to refund Public Utility, Revenue Subject To Refund Public Utility, Revenue Subject To Refund Power purchase agreements Power Purchase Agreements [Abstract] -- None. No documentation exists for this element. -- Number of power purchase agreements (PPAs) Number of Power Purchase Agreements Represents the number of firm power purchase agreements entered into, by the company. Power purchase capacity excluding agreements with smaller IPPs (in megawatts) Aggregate of Power Purchase Capacity Excluding Agreement with Smaller Independent Power Producers Represents the entity's aggregate capacity utilized under power purchase agreements (PPAs) excluding power purchase agreements with smaller independent power producers and schedule Q providers. Expected fixed capacity charges per year for 2018 through 2022, minimum Utilities Minimum Expected Fixed Capacity Charges Per Year, One Through Five Years Represents the minimum amount of expected fixed capacity charges per year for years one through five. Expected fixed capacity charges from 2023 through 2033 Utilities Expected Fixed Capacity Charges, After Five Through Fifteen Years Utilities Expected Fixed Capacity Charges, After Five Through Fifteen Years Purchase commitment, period Long-term Purchase Commitment, Period Purchase commitment, minimum power volume required to be purchased Long-term Purchase Commitment, Minimum Power Volume Required Long-term Purchase Commitment, Minimum Power Volume Required Purchase commitment, arbitration, additional capacity requirement Long Term Purchase Commitment, Arbitration, Additional Capacity Requirement Long Term Purchase Commitment, Arbitration, Additional Capacity Requirement Renewable projects Renewable Projects [Abstract] Renewable Projects [Abstract] ERP/EAM cost recovery cap Public Utility, ERP/EAM Cost Recovery Cap Public Utility, ERP/EAM Cost Recovery Cap ERP/EAM required pass-through savings Public Utility, ERP/EAM Required Pass-through Savings Over 12 Years Public Utility, ERP/EAM Required Pass-through Savings Over 12 Years ERP/EAM project service period (in years) Public Utility, ERP/EAM Project Service Period Public Utility, ERP/EAM Project Service Period Weighted average AFUDC rate Public Utilities, Allowance for Funds Used During Construction, Rate ERP/EAM implementation project costs Public Utilities, ERP/EAM Implementation Project Costs Public Utilities, ERP/EAM Implementation Project Costs ERP/EAM implementation project costs, operations and management Public Utilities, ERP/EAM Implementation Project Costs, Operations And Management Public Utilities, ERP/EAM Implementation Project Costs, Operations And Management ERP/EAM implementation project costs, capital costs Public Utilities, ERP/EAM Implementation Project Costs, Capital Costs Public Utilities, ERP/EAM Implementation Project Costs, Capital Costs ERP/EAM implementation project costs, deferred costs Public Utilities, ERP/EAM Implementation Project Costs, Deferred Costs Public Utilities, ERP/EAM Implementation Project Costs, Deferred Costs ERP/EAM implementation project costs, accrued carrying costs once put into service Public Utilities, ERP/EAM Implementation Project Costs, Accrued Carrying Costs Once Put Into Service Public Utilities, ERP/EAM Implementation Project Costs, Accrued Carrying Costs Once Put Into Service ERP/EAM implementation project, expected future O&M expense reductions Public Utility, ERP/EAM System, Future Operation And Maintenance Expense Reductions Public Utility, ERP/EAM System, Future Operation And Maintenance Expense Reductions ERP/EAM implementation project, future cost avoidance related to capital costs and tax costs Public Utility, ERP/EAM System, Future Cost Avoidance Related To Capital Cost And Tax Cost Public Utility, ERP/EAM System, Future Cost Avoidance Related To Capital Cost And Tax Cost Project facility capacity (in mW) Public Utility, Project Facility Capacity Public Utility, Project Facility Capacity Project, lease term (in years) Public Utility, Project, Lease Term Public Utility, Project, Lease Term Maximum project budget Public Utility, Maximum Project Budget Public Utility, Maximum Project Budget Percent of costs recoverable through recovery mechanisms other than base rates Public Utility, Project, Percent Of Cost Recoverable Through Recovery Mechanisms Other Than Base Rates Public Utility, Project, Percent Of Cost Recoverable Through Recovery Mechanisms Other Than Base Rates Total project costs incurred Public Utility, Project, Total Project Cost Incurred Public Utility, Project, Total Project Cost Incurred Amount recoverable through the major project interim recovery Public Utility, Maximum Project Budget, Effective Amount Recoverable Through The Major Project Interim Recovery Public Utility, Maximum Project Budget, Effective Amount Recoverable Through The Major Project Interim Recovery Environmental regulation Environmental Remediation Obligations [Abstract] Solar project, energy production (in megawatts) Public Utilities, Solar Project, Facility Energy Production