Weighted Average Shares Weighted Average Number of Shares Outstanding, Diluted [Abstract] Maximum Maximum [Member] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] UNS Gas Inc. UNS Gas Inc. [Member] UNS Gas Inc. [Member] Range [Domain] Statistical Measurement [Domain] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Carrying value Reported Value Measurement [Member] Diluted EPS Net Income (Loss) Available to Common Stockholders, Diluted Subsequent Event Subsequent Event [Member] Document Fiscal Year Focus Document Fiscal Year Focus UNS Electric Inc. UNS Electric Inc. [Member] UNS Electric Inc. Cash Collateral Posted/(Received) Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Offset Write-offs, net of recoveries Accounts Receivable, Allowance For Credit Loss, Write-Off Net Of Recoveries Accounts Receivable, Allowance For Credit Loss, Write-Off Net Of Recoveries ACC Arizona Corporation Commission [Member] Arizona Corporation Commission [Member] Other investments Other Assets, Fair Value Disclosure Customer [Axis] Customer [Axis] Segment Reporting [Abstract] Segment Reporting [Abstract] Common shares Common Stock, Value, Issued Realized gain on derivatives Realized Gain (Loss) On Derivatives Realized Gain (Loss) On Derivatives Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] Schedule of Long-Term Debt Schedule of Long-Term Debt Instruments [Table Text Block] Regulated Regulated Utilities Regulated Operation [Member] Employee Future Benefits Retirement Benefits [Text Block] Loss contingency accrual Loss Contingency Accrual Credit facility Line of Credit [Member] Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Derivative Instrument [Axis] Derivative Instrument [Axis] Long-Term Gas Transportation Precedent Agreements, 20-Year Agreement Long-Term Gas Transportation Precedent Agreements, 20-Year Agreement [Member] Long-Term Gas Transportation Precedent Agreements, 20-Year Agreement Regulatory liabilities (Note 6) Long-term regulatory liabilities Regulatory Liability, Noncurrent Amendment Flag Amendment Flag Current liabilities Liabilities, Current [Abstract] Accounts payable and other current liabilities Increase (Decrease) in Accounts Payable and Other Operating Liabilities Credit loss expense Accounts Receivable, Credit Loss Expense (Reversal) Schedule of Volume of Derivative Activity Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Tucson Electric Power Company Tucson Electric Power Company [Member] Tucson Electric Power Company [Member] Equity component, allowance for funds used during construction (Note 9) Equity component, allowance for funds used during construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity No one bank No One Bank [Member] No One Bank [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Deferred lease costs Deferred Lease Costs [Member] Deferred Lease Costs [Member] Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax [Abstract] Unsecured senior notes, April issuance, 2031 maturity Unsecured Senior Notes, April Issuance, 2031 Maturity [Member] Unsecured Senior Notes, April Issuance, 2031 Maturity Entity Address, State or Province Entity Address, State or Province Regulatory Matters Public Utilities Disclosure [Text Block] Assets Assets, Fair Value Disclosure [Abstract] Additions to property, plant and equipment and intangible assets Segment Reporting, Long-Lived Asset, Expenditure for Addition Intangible assets, net Intangible Asset, Excluding Goodwill, after Accumulated Amortization Notional amount Derivative, Notional Amount Basic EPS (shares) Weighted Average Number of Shares Outstanding, Basic Retirement Benefits [Abstract] Retirement Benefits [Abstract] Non-cash financing activity Cash Flow, Noncash Financing Activities [Abstract] Cash Flow, Noncash Financing Activities Regulatory assets (Note 6) Long-term regulatory assets Regulatory Asset, Noncurrent FortisBC Electric FortisBC Electric Inc. [Member] FortisBC Inc. [Member] Total current liabilities Liabilities, Current Contribution to equity-accounted investee Payments to Acquire Additional Interest in Subsidiaries Regulatory Liability [Axis] Regulatory Liability [Axis] Regulatory adjustments Defined Benefit Plan, Regulatory Adjustments Defined Benefit Plan, Regulatory Adjustments Credit loss deferral Accounts Receivable, Allowance For Doubtful Accounts Receivable, Credit Loss Deferral Accounts Receivable, Allowance For Doubtful Accounts Receivable, Credit Loss Deferral Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Entity Address, City or Town Entity Address, City or Town Schedule of Supplementary Cash Flow Information Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Receivables [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] ITC ITC Holdings Corp. [Member] ITC Holdings Corp. [Member] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Preference shares Payments of Ordinary Dividends, Preferred Stock and Preference Stock Net earnings attributable to common equity shareholders Basic EPS Net Income (Loss) Available to Common Stockholders, Basic Accounts receivable and other current assets (Note 5) Accounts and Other Receivables, Net, Current Level 2 Fair Value, Inputs, Level 2 [Member] Total credit facilities Line of Credit Facility, Maximum Borrowing Capacity Other comprehensive income (loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Current installments of long-term debt (Note 7) Less: Current installments of long-term debt Current installments of long-term debt Long-Term Debt, Current Maturities Revenue Revenue Benchmark [Member] Central Hudson Central Hudson Gas and Electric Corporation [Member] Central Hudson Gas and Electric Corporation [Member] Dividends on preference shares Dividends, Preferred Stock Subsequent Event Type [Axis] Subsequent Event Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Manufactured gas plant site remediation deferral Environmental Restoration Costs [Member] Future Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Litigation Case [Axis] Litigation Case [Axis] Fair Value, Concentration of Risk [Table] Fair Value, Concentration of Risk [Table] Accrued capital expenditures Capital Expenditures Incurred but Not yet Paid Renewable Power Purchase Agreement Renewable Power Purchase Agreement [Member] Renewable Power Purchase Agreement Secured senior notes, January issuance, 2046 maturity Secured Senior Notes, January Issuance, 2046 Maturity [Member] Secured Senior Notes, January Issuance, 2046 Maturity Schedule of Information by Reportable Segment Segment Reporting [Table Text Block] Non-Controlling Interests 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Subsidiary dividends paid to non-controlling interests Payments of Ordinary Dividends, Noncontrolling Interest Derivative interest rate Derivative, Fixed Interest Rate Energy contracts Energy Related Derivative [Member] Gains (losses) on derivatives Unrealized Gain (Loss) on Derivatives EPS Earnings Per Share, Diluted [Abstract] Schedule of Regulatory Assets [Table] Regulated Operation, Regulatory Asset [Table] Potential dilutive effect of stock-based compensation Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units Controlling ownership interest Subsidiary, Ownership Percentage, Parent Long-term purchase commitment, amount Long-Term Purchase Commitment, Amount Long-term debt Long-term debt (including current portion) Long-Term Debt, Gross Meter cost recovery Advanced Metering Infrastructure Costs [Member] Credit Facility [Domain] Credit Facility [Domain] Operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Diluted EPS (shares) Weighted Average Number of Shares Outstanding, Diluted Allowance for Credit Losses Allowance for Credit Losses [Text Block] Foreign exchange contracts and cross-currency interest rate swaps Cross Currency Interest Rate Contract [Member] First mortgage bonds, March issuance, 2034 maturity First Mortgage Bonds, March Issuance, 2034 Maturity [Member] First Mortgage Bonds, March Issuance, 2034 Maturity Deferred income taxes Deferred Income Tax Charge [Member] Disposal Group Name [Domain] Disposal Group Name [Domain] Line of Credit Facility [Table] Line of Credit Facility [Table] Other Other Comprehensive Income, Other, Net of Tax Borrowings under committed credit facilities Proceeds from Lines of Credit Posted/Received Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return (Receive) Cash, Offset Against Derivative Asset Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return (Receive) Cash, Offset Against Derivative Asset Regulatory Asset [Axis] Regulatory Asset [Axis] Wataynikaneyap Power Limited Partnership Wataynikaneyap Power Limited Partnership [Member] Wataynikaneyap Power Limited Partnership [Member] Short-term borrowings (Note 7) Short-term borrowings Short-Term Debt Derivatives, period over which gains (losses) will be reclassified to earnings Derivative, Gains (Losses) To Be Reclassified To Earnings, Period Derivative, Gains (Losses) To Be Reclassified To Earnings, Period Letters of credit outstanding Letters of Credit Outstanding, Amount Property, plant and equipment, net Public Utilities, Property, Plant and Equipment, Net Comprehensive income (loss) attributable to: Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Level 1 Fair Value, Inputs, Level 1 [Member] Belize Electricity Belize Electricity Limited [Member] Belize Electricity Limited [Member] Contributions in aid of construction Proceeds from Contribution in Aid of Construction, Investing Activity Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Potential dilutive effect of stock-based compensation (shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Regulated Operations [Abstract] Regulated Operations [Abstract] Long-term debt, including current portion Long-Term Debt, Fair Value Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Depreciation - property, plant and equipment Depreciation Scenario [Domain] Scenario [Domain] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Inter-segment loans Intersegment Loans, Amount Intersegment Loans, Amount Change in long-term regulatory assets and liabilities Increase (Decrease) In Regulatory Assets And Liabilities, Noncurrent Increase (Decrease) In Regulatory Assets And Liabilities, Noncurrent Schedule of Net Earnings to Common Shareholders Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Segmented Information Segment Reporting [Text Block] Common shares, net of dividends reinvested Payments of Ordinary Dividends, Common Stock Unrealized gains (losses) on energy contracts Unrealized Gain (Loss) on Energy Contracts Hedging Relationship [Axis] Hedging Relationship [Axis] Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Counterparty Netting of Energy Contracts Derivative Asset, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Total equity Balance, beginning of period Balance, end of period 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swaps and foreign exchange contracts Cross-Currency Interest Rate Swaps And Foreign Exchange Contracts [Member] Cross-Currency Interest Rate Swaps And Foreign Exchange Contracts Credit facilities utilized: Line of Credit Facility [Abstract] Secured Secured Debt [Member] Foreign exchange contracts Foreign Exchange Contract [Member] Total expenses Costs and Expenses Site Contingency [Table] Site Contingency [Table] Schedule of Other Income, Net Schedule of Other Nonoperating Income (Expense) [Table Text Block] Interest rate Debt Instrument, Interest Rate, Stated Percentage Shareholders' equity Equity, Attributable to Parent Unsecured committed revolving credit facilities Unsecured Committed Revolving Credit Facilities [Member] Unsecured Committed Revolving Credit Facilities Unsecured senior notes, April issuance, 2041 maturity Unsecured Senior Notes, April Issuance, 2041 Maturity [Member] Unsecured Senior Notes, April Issuance, 2041 Maturity Other income, net (Note 9) Other income, net 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Income (Expense), Nonoperating Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Accounts receivable and other current assets Increase (Decrease) in Accounts Receivable and Other Operating Assets Entity Central Index Key Entity Central Index Key Regulatory Liabilities [Line Items] Regulatory Liability [Line Items] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Other Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Cash from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation FortisTCI FortisTCI [Member] FortisTCI Business development deposit tax Business Development Deposit Tax [Member] Business Development Deposit Tax Other Stockholders' Equity, Other Income Statement [Abstract] Income Statement [Abstract] Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Energy efficiency liability Energy Efficiency Liability [Member] Energy Efficiency Liability [Member] Investment, Name [Axis] Investment, Name [Axis] Approved return on equity, allowable range Public Utilities, Approved Return on Equity, Allowable Range Public Utilities, Approved Return on Equity, Allowable Range Designated as hedging instrument Designated as Hedging Instrument [Member] Finance leases Finance Lease, Liability, Noncurrent Inter-segment eliminations Intersegment Eliminations [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Wholesale trading contracts, Energy contracts not subject to regulatory deferral Wholesale Trading Contracts, Not Subject to Regulatory Deferral [Member] Wholesale Trading Contracts, Not Subject to Regulatory Deferral[Member] Deferred energy management costs Deferred Project Costs [Member] Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] Fair Value, Concentration of Risk, Financial Statement Captions [Line Items] Employee future benefits Pension and Other Postretirement Plans Costs [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] FortisBC Energy Fortis BC Energy Inc. [Member] Fortis BC Energy Inc. [Member] Statement [Line Items] Statement [Line Items] Total assets Total assets Assets Volume (gwh / gj) Derivative, Nonmonetary Notional Amount, Energy Measure Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Entity [Domain] Entity [Domain] Net earnings attributable to: Income Amounts Attributable to Parent, Disclosures [Abstract] Total return swaps and interest rate contracts Total Return Swaps And Interest Rate Contracts [Member] Total Return Swaps And Interest Rate Contracts Amortization of past service credits/plan amendments Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Operating segments Operating Segments [Member] Finance charges Finance charges Interest Expense, Nonoperating Fortis Fortis Inc. [Member] Fortis Inc. [Member] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Common shares issued (shares) Stock Issued During Period, Shares, New Issues Accounts payable and other current liabilities Accounts Payable and Other Accrued Liabilities, Current Balance, beginning of period (shares) Balance, end of period (shares) Shares, Outstanding Prepaid expenses Increase (Decrease) in Prepaid Expense Measurement Basis [Axis] Measurement Basis [Axis] Gross Amount Recognized in Balance Sheet Derivative Asset, Subject to Master Netting Arrangement, Liability Offset Other liabilities Other Liabilities, Noncurrent Goodwill Goodwill Goodwill Retirement Plan Type [Axis] Retirement Plan Type [Axis] Counterparty Netting of Energy Contracts Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Unhedged foreign net investments Net Investment In Foreign Operation, Amount Not Hedged Net Investment In Foreign Operation, Amount Not Hedged Caribbean Utilities Caribbean Utilities Company, Ltd. [Member] Caribbean Utilities Company, Ltd. [Member] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings Retained Earnings [Member] Operating expenses Operating expenses Operating Expenses ATM Program, remaining amount available At-The-Market Equity Program, Remaining Amount Available At-The-Market Equity Program, Remaining Amount Available Increase (Decrease) in Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Diluted (CAD per share) Earnings Per Share, Diluted Cash from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Bank concentration risk Lender Concentration Risk [Member] Change in working capital (Note 12) Changes in working capital Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital Liabilities Liabilities, Fair Value Disclosure [Abstract] Litigation Case [Domain] Litigation Case [Domain] Three customers Three Customers [Member] Three Customers [Member] Net change in short-term borrowings Proceeds from (Repayments of) Short-Term Debt, Maturing in Three Months or Less Amortization - intangible assets Intangible Asset, Finite-Lived, Amortization Expense Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Ownership [Domain] Ownership [Domain] Adjustments to reconcile net earnings to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Schedule of Derivative Offset Netting, Assets Offsetting Assets [Table Text Block] Financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Credit facilities unutilized Line of Credit Facility, Remaining Borrowing Capacity Interest costs Defined Benefit Plan, Interest Cost Regulatory Assets [Line Items] Regulatory Asset [Line Items] Derivative assets Derivative Asset Non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Estimated fair value Estimate of Fair Value Measurement [Member] Common shares issued Stock Issued During Period, Value, New Issues Prepaid expenses Prepaid Expense, Current Net Amount Derivative Liability, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Long-term debt, excluding credit facility borrowings Long-Term Debt Excluding Credit Facilities Long-Term Debt Excluding Credit Facilities Preference Shares Preferred Stock [Member] Inventories Increase (Decrease) in Inventories Other Payment for (Proceeds from) Other Investing Activity Short-form base shelf prospectus, life Short-form Base Shelf Prospectus, Life Term Short-form Base Shelf Prospectus, Life Term Common share dividends reinvested Stock Issued Segment Reporting [Table] Segment Reporting [Table] Foreign exchange Accounts Receivable, Allowance For Doubtful Accounts, Foreign Currency Translation Accounts Receivable, Allowance For Doubtful Accounts, Foreign Currency Translation Schedule of Equity Method Investments [Table] Equity Method Investment [Table] Long-term debt (including current portion), weighted average interest rate (percent) Long-Term Debt, Weighted Average Interest Rate, at Point in Time Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Operating income Operating Income (Loss) Current Fiscal Year End Date Current Fiscal Year End Date Wappingers Falls Lawsuit Wappingers Falls Lawsuit [Member] Wappingers Falls Lawsuit Sale of investment tax credits Gain (Loss) Sale Of Investment Tax Credits Gain (Loss) Sale Of Investment Tax Credits Dividends declared on common shares (CAD per share) Common Stock, Dividends, Per Share, Declared Entity File Number Entity File Number Change in working capital Additional Cash Flow Elements, Operating Activity [Abstract] Service costs Defined Benefit Plan, Service Cost Subsidiary dividends paid to non-controlling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders UNS Energy UNS Energy Corporation [Member] UNS Energy Corporation [Member] Common stock, shares issued (in shares) Common Stock, Shares, Issued Electricity swap contracts, Energy contracts subject to regulatory deferral Electricity Swap Contracts, Subject to Regulatory Deferral [Member] Electricity Swap Contracts, Subject to Regulatory Deferral [Member] Description of Business Business Description and Basis of Presentation [Text Block] Equity Components [Axis] Equity Components [Axis] Debt, redeemed amount Debt Instrument, Repurchase Amount Non-controlling interests Net Income (Loss) Attributable to Noncontrolling Interest First mortgage bonds, March issuance, 2035 maturity First Mortgage Bonds, March Issuance, 2035 Maturity [Member] First Mortgage Bonds, March Issuance, 2035 Maturity Deferred income taxes Deferred Income Tax Liabilities, Net Defined contribution plan cost recognized Defined Contribution Plan, Cost Common equity shareholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Unsecured senior notes, April issuance, 2046 maturity Unsecured Senior Notes, April Issuance, 2046 Maturity [Member] Unsecured Senior Notes, April Issuance, 2046 Maturity Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Dispositions Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Energy contracts not subject to regulatory deferral Energy Related Derivatives Not Subject to Regulatory Deferral [Member] Energy Related Derivatives Not Subject to Regulatory Deferral [Member] Net Amount Derivative Asset, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Other assets Other Assets, Noncurrent Line of Credit Facility, Lender [Domain] Line of Credit Facility, Lender [Domain] Document Type Document Type 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Electricity power purchase contracts, Energy contracts subject to regulatory deferral Electricity Power Purchase Contracts, Subject to Regulatory Deferral [Member] Electricity Power Purchase Contracts, Subject to Regulatory Deferral [Member] OPEB Plans Other Postretirement Benefits Plan [Member] Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Amortization - other Amortization of Other Deferred Charges Energy contracts subject to regulatory deferral Energy Related Derivatives Subject to Regulatory Deferral [Member] Energy Related Derivatives Subject to Regulatory Deferral [Member] Foreign net investments Net Investment Hedging [Member] Approved equity component of capital structure Public Utilities, Approved Equity Capital Structure, Percentage Earnings before income tax expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest 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Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Other, income tax expense (recovery) Other Comprehensive Income (Loss), Other, Tax Other Comprehensive Income (Loss), Other, Tax Derivative Instruments and Hedging Activities Disclosures [Table] Derivative Instruments and Hedging Activities Disclosures [Table] Allowance for Credit Losses [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Legal Entity [Axis] Legal Entity [Axis] Regulation Status [Axis] Regulation Status [Axis] Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Long-term credit facility borrowings Long-term Credit Facility Borrowings [Member] Long-term Credit Facility Borrowings [Member] Deferred restoration costs Storm Restoration Costs [Member] Storm Restoration Costs Inventories Public Utilities, Inventory Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Equity investment ownership Equity investment ownership Equity Method Investment, Ownership Percentage Gas swap contracts, Energy contracts subject to regulatory deferral Gas Swap Contracts, Subject to Regulatory Deferral [Member] Gas Swap Contracts, Subject to Regulatory Deferral [Member] Regulated and Unregulated Operation [Domain] Regulated and Unregulated Operation [Domain] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Disposal Group Name [Axis] Disposal Group Name [Axis] Number of reportable segments not disclosed Number Of Reportable Segments Not Disclosed, Flag Number Of Reportable Segments Not Disclosed, Flag Related party transactions Related Party Transaction, Amounts of Transaction Customer [Domain] Customer [Domain] Investment, Name [Domain] Investment, Name [Domain] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Basic (CAD per share) Earnings Per Share, Basic Schedule of Regulatory Liabilities [Table] Regulated Operation, Regulatory Liability [Table] Total current assets Assets, Current Range [Axis] Statistical Measurement [Axis] Central Hudson Central Hudson [Member] Central Hudson Repayments of long-term debt and finance leases Repayment of Long-Term Debt, Long-Term Lease Obligation, and Capital Security Long-term debt (Note 7) Long-term debt less current portion and deferred financing costs and debt discounts Long-Term Debt, Excluding Current Maturities Derivatives Deferred Derivative Gain (Loss) [Member] Retained earnings Retained Earnings (Accumulated Deficit) Depreciation Rates Depreciation Rates [Member] Depreciation Rates Defined Benefit Pension Plans Pension Plan [Member] Common Shares Common Stock [Member] Earnings from disposition Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Fair Value Measurement [Domain] Fair Value Measurement [Domain] Cover [Abstract] Gas supply contract, Energy contracts subject to regulatory deferral Gas Supply Contract, Subject to Regulatory Deferral [Member] Gas Supply Contract Premiums, Subject to Regulatory Deferral Member] Short-form base shelf prospectus, principal amount, up to Short-form Base Shelf Prospectus, Principal Amount, Maximum Short-form Base Shelf Prospectus, Principal Amount, Maximum Short-term borrowings, weighted average interest rate (percent) Short-Term Debt, Weighted Average Interest Rate, at Point in Time Concentration risk percentage Concentration Risk, Percentage Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Derivative Contract [Domain] Derivative Contract [Domain] FortisAlberta Fortis Alberta Inc. [Member] Fortis Alberta Inc. [Member] Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Hedging Relationship [Domain] Hedging Relationship [Domain] Total liabilities and equity Liabilities and Equity Regulatory Asset [Domain] Regulatory Asset [Domain] Non-controlling interests Equity, Attributable to Noncontrolling Interest Segments [Axis] Segments [Axis] Additional paid-in capital Additional Paid in Capital Other Other Nonoperating Income (Expense) Additions to intangible assets Payments to Acquire Intangible Assets Long-Term Debt Long-Term Debt [Text Block] Realized gains, portion shared with customers (percent) Realized Gains Shared With Customers, Percent Realized Gains Shared With Customers, Percent Equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Entity Address, Country Entity Address, Country Fair Value of Financial Instruments and Risk Management Derivatives and Fair Value [Text Block] Preference equity shareholders Preference equity shareholders Preferred Stock Dividends and Other Adjustments Unsecured senior notes, 2029 maturity Unsecured Senior Notes, 2029 Maturity, Fortis [Member] Unsecured Senior Notes, 2029 Maturity, Fortis Regulatory liability Total regulatory liabilities Total regulatory liabilities Regulatory Liability Dividends Payments of Ordinary Dividends [Abstract] Preference shares Preferred Stock, Value, Issued Hedging Designation [Domain] Hedging Designation [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Credit Facility [Axis] Credit Facility [Axis] Assets, fair value Assets, Fair Value Disclosure Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Discontinued Operations and Disposal Groups [Abstract] Discontinued Operations and Disposal Groups [Abstract] Non-Regulated Corporate and Other Unregulated Operation [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Unsecured senior notes, July issuance, 2056 maturity Unsecured Senior Notes, July Issuance, 2056 Maturity [Member] Unsecured Senior Notes, July Issuance, 2056 Maturity Debt Instrument [Line Items] Debt Instrument [Line Items] Short-form base shelf prospectus, remaining amount available Short-form Base Shelf Prospectus, Remaining Amount Available Short-form Base Shelf Prospectus, Remaining Amount Available Corporate and Other Corporate Segment and Other Operating Segment [Member] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Additional Paid-In Capital Additional Paid-in Capital [Member] Supplemental Cash Flow Elements [Abstract] Supplemental Cash Flow Elements [Abstract] Other regulatory assets Other regulatory liabilities Other Regulatory Assets (Liabilities) [Member] Schedule of Derivative Offset Netting, Liabilities Offsetting Liabilities [Table Text Block] Schedule of Regulatory Assets Schedule of Regulatory Assets [Table Text Block] Future cost of removal Removal Costs [Member] Cash and cash equivalents Cash and Cash Equivalent First mortgage bonds, July issuance, 2047 maturity First Mortgage Bonds, July Issuance, 2047 Maturity [Member] First Mortgage Bonds, July Issuance, 2047 Maturity Gain on derivatives, net Gain (Loss) on Derivative Instruments, Net, Pretax ATM Program, principal amount, maximum At-The-Market Equity Program, Principal Amount, Maximum At-The-Market Equity Program, Principal Amount, Maximum Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Fortis Belize and Belize Electricity Fortis Belize and Belize Electricity [Member] Fortis Belize and Belize Electricity Depreciation and amortization Depreciation, Depletion and Amortization Total return swaps Total Return Swap [Member] Entity Address, Address Line Three Entity Address, Address Line Three Entity Address, Address Line Two Entity Address, Address Line Two Net earnings Net earnings Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Current assets Assets, Current [Abstract] Derivative liabilities Derivative Liability Secured senior notes, January issuance, 2036 maturity Secured Senior Notes, January Issuance, 2036 Maturity [Member] Secured Senior Notes, January Issuance, 2036 Maturity Entity Address, Address Line One Entity Address, Address Line One Income tax expense Income tax expense Income Tax Expense (Benefit) Other Income, Net Other Income and Other Expense Disclosure [Text Block] Customer concentration risk Customer Concentration Risk [Member] Regulatory assets - current portion Increase (Decrease) in Other Regulatory Assets Energy supply costs Cost of Product and Service Sold Change in cash and cash equivalents Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forecast Forecast [Member] First mortgage bonds, July issuance, 2044 maturity First Mortgage Bonds, July Issuance, 2044 Maturity [Member] First Mortgage Bonds, July Issuance, 2044 Maturity Amortization of actuarial gains Defined Benefit Plan, Amortization of Gain (Loss) Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Statement [Table] Statement [Table] Total return swaps and foreign exchange contracts Total Return Swaps And Foreign Exchange Contracts [Member] Total Return Swaps And Foreign Exchange Contracts Approved ROE Public Utilities, Approved Return on Equity, Percentage Regulatory liabilities (Note 6) Less: Current portion Regulatory Liability, Current Derivative terms Derivative, Contract Term Derivative Instruments and Hedging Activities Disclosures [Line Items] Derivative Instruments and Hedging Activities Disclosures [Line Items] Gross Amount Recognized in Balance Sheet Derivative Asset, Subject to Master Netting Arrangement, before Offset Category of Item Purchased [Axis] Category of Item Purchased [Axis] General Rate Application General Rate Application [Member] General Rate Application Net Earnings to Common Shareholders Net Income (Loss) Available to Common Stockholders, Diluted [Abstract]