75000 - Document - Cover Page
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75010 - Statement - CONSOLIDATED STATEMENTS OF EARNINGS
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75020 - Statement - CONSOLIDATED BALANCE SHEETS
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75030 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)
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75040 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS
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75050 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY
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75060 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (Parenthetical)
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75070 - Disclosure - Cybersecurity Risk Management, Strategy, and Governance
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995455 - Disclosure - Summary of Significant Accounting Policies
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995465 - Disclosure - Segment Information
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995475 - Disclosure - Allowance for Doubtful Accounts
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995485 - Disclosure - Debt and Financing Arrangements
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995495 - Disclosure - Equity
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995505 - Disclosure - Energy Supply
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995515 - Disclosure - Derivatives
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995525 - Disclosure - Commitments and Contingencies
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995535 - Disclosure - Income Taxes
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995545 - Disclosure - Retirement Benefit Plans
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995555 - Disclosure - Summary Of Significant Accounting Policies (Policies)
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995565 - Disclosure - Summary of Significant Accounting Policies (Tables)
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995575 - Disclosure - Segment Information (Tables)
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995585 - Disclosure - Allowance for Doubtful Accounts (Tables)
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995595 - Disclosure - Debt and Financing Arrangements (Tables)
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995605 - Disclosure - Equity (Tables)
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995615 - Disclosure - Commitments and Contingencies (Tables)
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995625 - Disclosure - Income Taxes (Tables)
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995635 - Disclosure - Retirement Benefit Plans (Tables)
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995645 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details)
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995655 - Disclosure - Summary of Significant Accounting Policies - Components of Gas and Electric Operating Revenue (Details)
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995665 - Disclosure - Summary of Significant Accounting Policies - Components of Accrued Revenue (Detail)
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995675 - Disclosure - Summary of Significant Accounting Policies - Components of Exchange Gas Receivable (Detail)
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995685 - Disclosure - Summary of Significant Accounting Policies - Components of Gas Inventory (Detail)
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995695 - Disclosure - Summary of Significant Accounting Policies - Regulatory Assets (Detail)
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995705 - Disclosure - Summary of Significant Accounting Policies - Regulatory Liabilities (Detail)
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995715 - Disclosure - Summary of Significant Accounting Policies - Fair Value of Marketable Securities (Detail)
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995725 - Disclosure - Summary of Significant Accounting Policies - Components of Energy Supply Obligations (Detail)
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995735 - Disclosure - Segment Information - Significant Segment Financial Data (Detail)
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995745 - Disclosure - Segment Information (Additional Information) (Details)
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995755 - Disclosure - Allowance for Doubtful Accounts - Additional Information (Detail)
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995765 - Disclosure - Activity in Company's Allowance for Doubtful Accounts (Detail)
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995775 - Disclosure - Debt and Financing Arrangements - Additional Information (Detail)
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995785 - Disclosure - Debt and Financing Arrangements - Schedule Of Carrying Values And Estimated Fair Values Of Debt Instruments (Details)
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995795 - Disclosure - Debt and Financing Arrangements - Details on Long Term Debt (Detail)
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995805 - Disclosure - Debt and Financing Arrangements- Details on Long Term Debt (Parenthetical) (Detail)
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995815 - Disclosure - Debt and Financing Arrangements - Summary of Interest Expense and Interest Income (Detail)
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995825 - Disclosure - Debt and Financing Arrangements - Borrowing Limits Amounts Outstanding and Amounts Available under Revolving Credit Facility (Detail)
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995835 - Disclosure - Debt and Financing Arrangements - Summary of Contractual Obligations for Long-term Debt (Detail)
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995845 - Disclosure - Debt and Financing Arrangements - Classification of the Company Lease Obligations (Detail)
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995855 - Disclosure - Debt and Financing Arrangements - Future Operating Lease Payment Obligations and Future Minimum Lease Payments under Capital Leases (Detail)
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995865 - Disclosure - Debt and Financing Arrangements - Future Operating Lease Payment Obligations and Future Minimum Lease Payments under Capital Leases (Detail) 4
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995875 - Disclosure - Equity - Additional Information (Detail)
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995885 - Disclosure - Equity - Schedule of Common Shares Activity (Details)
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995895 - Disclosure - Equity - Restricted Shares Issued in Conjunction with Stock Plan (Detail)
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995905 - Disclosure - Equity - Time Restricted Shares and Performance Restricted Shares activity (Details)
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995915 - Disclosure - Equity - Restricted Stock Units Issued (Detail)
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995925 - Disclosure - Equity - Reconciles Basic and Diluted Earnings Per Share (Detail)
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995935 - Disclosure - Equity - Weighted Average Non Vested Restricted Shares Excluded from Computation of Earnings Per Share (Detail)
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995945 - Disclosure - Energy Supply - Additional Information (Detail)
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995955 - Disclosure - Derivatives (Additional Information) (Details)
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995965 - Disclosure - Commitments and Contingencies - Gas And Electric Supply Contractual Obligations (Detail)
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995975 - Disclosure - Commitments and Contingencies - Additional Information (Detail)
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995985 - Disclosure - Commitments and Contingencies - Company's Liability for Environmental Obligations (Detail)
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995995 - Disclosure - Income Taxes - Provisions for Federal and State Income Taxes (Detail)
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996005 - Disclosure - Income Taxes - Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate (Detail)
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996015 - Disclosure - Income Taxes - Income taxes paid, net of refunds (Details)
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996025 - Disclosure - Income Taxes - Deferred Tax Assets and Liabilities (Detail)
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996035 - Disclosure - Income Taxes - Deferred Tax Assets and Liabilities (Parenthetical) (Details)
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996045 - Disclosure - Income Taxes - Additional Information (Detail)
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996055 - Disclosure - Retirement Benefit Plans - Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations (Detail)
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996065 - Disclosure - Retirement Benefit Plans - Additional Information (Detail)
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996075 - Disclosure - Retirement Benefit Plans - Components of Retirement Plan Costs (Detail)
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996085 - Disclosure - Retirement Benefit Plans - Summary of Information on Plans' Assets, Projected Benefit Obligations (PBO), and Funded Status (Detail)
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996095 - Disclosure - Retirement Benefit Plans - Employer Contributions, Participant Contributions and Benefit Payments (Detail)
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996105 - Disclosure - Retirement Benefit Plans - Estimated Future Benefit Payments (Detail)
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996115 - Disclosure - Retirement Benefit Plans - Actual Investment Allocations (Detail)
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996125 - Disclosure - Retirement Benefit Plans - Assets Measured at Fair Value on Recurring Basis for Pension Plan (Detail)
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996135 - Disclosure - Retirement Benefit Plans - Assets Measured at Fair Value on Recurring Basis for PBOP Plan (Detail)
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Fixed Income Funds
Fixed Income Funds [Member]
Business Combination, Acquisition-Related Cost, Expense
Acquisition amount
Regulated Operation, Inventory [Table]
New Hampshire
NEW HAMPSHIRE
Defined Benefit Plans Type Of Plans
Retirement Plan Type [Axis]
Non Vested Restricted Stock Member
Non Vested Restricted Stock
Non Vested Restricted Stock [Member]
Segments [Domain]
Federal Tax Credit Carryforward
Federal Tax Credit Carryforward
Dividend declared
Dividends, Preferred Stock
Dividends, Preferred Stock, Total
Environmental Matters
Environmental Costs, Policy [Policy Text Block]
3.52% Senior Notes, Due November 1, 2027
Senior Notes Three Point Five Two Percent Due November One Twenty Twenty Seven [Member]
Senior Notes Three Point Five Two Percent Due November One Twenty Twenty Seven [Member]
Finance Lease, Liability, Total
Finance Lease, Liability
Total Capital Lease Obligations
July 1, 2024 [Member]
July First Two Thousand And Twenty Four [Member]
July First Two Thousand And Twenty Four Member
Deferred Tax Assets
Deferred Tax Assets, Gross [Abstract]
Entity Incorporation, State or Country Code
Finance Lease, Liability, to be Paid, Year Four
2029
Statement of Financial Position Location, Balance [Domain]
Purchases of natural gas, contract duration
Contract Duration
Contract duration.
Program duration
Revenue Increase Approved By Regulator
Revenue Increase Approved By Regulator
Revenue increase approved by regulator
Employer Contributions
Defined Benefit Plan, Plan Assets, Contributions by Employer
Accounts Payable
Increase (Decrease) in Accounts Payable
Increase (Decrease) in Accounts Payable, Total
Allowance For Doubtful Accounts Abstract
Allowance For Doubtful Accounts [Abstract]
Long-Term Debt, Less Current Portion
Total Long-Term Debt, Less Current Portion
Long-Term Debt, Excluding Current Maturities
Long-Term Debt, Excluding Current Maturities, Total
Details on Long Term Debt
Schedule of Long-Term Debt Instruments [Table Text Block]
Deductible portion of goodwill
Business Combination, Goodwill, Expected Tax Deductible, Amount
Equity [Abstract]
Entity Current Reporting Status
Receivables Billing Status [Domain]
Receivables Billing Status [Domain]
Regulatory liability, expected flow back to customers
Regulatory Liability Recovery Refund
Regulatory liability recovery refund.
Operating Expenses [Abstract]
Operating Expenses:
Fair Value, Inputs, Level 2 [Member]
Fair Value Inputs Level 2
Commitments and Contingencies
Commitments and Contingencies Disclosure [Text Block]
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Amount
Regulatory Amortization of Excess ADIT
Common stock, shares authorized
Common Stock, Shares Authorized
RSU Settlement [Member]
RSU Settlement Member
RSU Settlement
MASSACHUSETTS
Cost of issue
Cost Of Issue
Cost Of Issue
Capitalization:
Capitalization, Long-Term Debt and Equity [Abstract]
Product and Service [Axis]
Oil and Gas, Acreage [Table]
Fair Value by Liability Class [Domain]
Document Fiscal Period Focus
ISO New England markets
ISO New England markets [Member]
ISO New England markets [Member]
Increase Decrease In Gas Inventory Financing
The net change during the reporting period in exchange gas financing.
Net Increase (Decrease) in Exchange Gas Financing
Finance Lease, Liability, to be Paid, Total
Finance Lease, Liability, to be Paid
Total Payments
Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years
2031-2035
Expected Long-term rate of return on plan assets
Defined Benefit Plan, Expected Long-term Return on Assets
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets
Program [Axis]
Program [Axis]
Fitchburg Grid Modernization [Member]
Fitchburg Grid Modernization [Member]
Fitchburg Grid Modernization
Long-term debt, stated interest rate
Stated interest rate
Debt Instrument, Interest Rate, Stated Percentage
First Mortgage Bonds Four Point Eighteen Percent Senior Secured Notes Due November Thirty Twenty Forty Eight [Member]
First Mortgage Bonds 4.18% Senior Secured Notes Due November 30, 2048
First Mortgage Bonds Four Point Eighteen Percent Senior Secured Notes Due November Thirty Twenty Forty Eight [Member]
Beginning Restricted Stock Units
Ending Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fully Vested Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Fully Vested, Weighted Average Grant Date Fair Value
Entity Shell Company
Spending cap
Total
Total
Contractual Obligation
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Unitil Service; Unitil Realty; and Unitil Resources
Other Subsidiaries [Member]
Other Subsidiaries [Member]
Order [Domain]
Order [Domain]
Regulatory Liabilities
Schedule of Regulatory Liabilities [Table Text Block]
Cash and Cash Equivalents
Cash and Cash Equivalent
Cash and Cash Equivalents, at Carrying Value, Total
PBO at Beginning of Year
PBO at End of Year
Defined Benefit Plan, Benefit Obligation
Defined Benefit Plan, Expected Future Benefit Payment, Year Two
2027
Cybersecurity Risk Management, Strategy, and Governance [Abstract]
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]
Cybersecurity Risk Board of Directors Oversight [Text Block]
Short-Term Debt [Table]
Statement [Table]
Energy [Axis]
Right-of-Use Assets Obtained in Exchange for Lease Obligations
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability
Electric
Electric
Electric [Member]
Electric [Member]
Regulatory Liability [Axis]
Gas Inventory
Weighted average cost inventory amount
Weighted Average Cost Inventory Amount
Deferred Compensation Plan [Member]
Deferred Compensation Plan [Member]
Deferred Compensation Plan [Member]
Deferred Compensation Plan
Second Amended Credit Facility
Second Amended Credit Facility [Member]
Second Amended Credit Facility [Member]
Statement [Line Items]
Utility Revenue Recognition
Utility, Revenue and Expense Recognition, Policy [Policy Text Block]
Trading Securities
Investments in trading securities
Debt Securities, Trading, and Equity Securities, FV-NI
Debt Securities, Trading, and Equity Securities, FV-NI, Total
Energy Supply Obligations
Supply Commitment [Policy Text Block]
It represents Supply Commitment.
Gas
Gas
Gas [Member]
Gas [Member]
Entity Filer Category
GSEP Two Thousand Twenty Seven [Member]
GSEP Two Thousand Twenty Seven [Member]
GSEP Two Thousand Twenty Seven
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques Tabl Table
Fair Value Measurement Inputs and Valuation Techniques [Table]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques Tabl [Table]
Acquisition of Maine Natural Gas Company Policy Text Block
Acquisition of Maine Natural Gas Company Policy Text Block
Acquisition of Maine Natural Gas Corporation
Reaches Ultimate Trend Rate Year
Reaches Ultimate Trend Rate Year
TOTAL LIABILITIES AND CAPITALIZATION
Liabilities and Equity
Debt Instrument [Line Items]
Debt Instrument [Line Items]
Long-Term Debt, Current Portion
Less: Current Portion
Long-Term Debt, Current Maturities
Long-Term Debt, Current Maturities, Total
Long-Term Debt, Maturity, Year Three
Debt repayment, 2028
Restructuring Type [Axis]
Long-Lived Tangible Asset [Axis]
Extended Renwel Periods
Extended Renwel Periods
Extended long-term renewable contracts
Finance Lease, Liability, to be Paid, Year Three
2028
Components of Gas and Electric Operating Revenue
Components Of Gas Operating Revenue And Electric Operating Revenue [Table Text Block]
Components of gas operating revenue and electric operating revenue.
Net Utility Plant
Net Utility Plant
Public Utilities, Property, Plant and Equipment, Net
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]
Long Term Debt Comprising Principal And Interest [Member]
Long Term Debt Comprising Principal And Interest [Member]
Long term debt comprising principal and interest.
Exercise Price Range [Axis]
Gain on divestiture of business, net
Net Gain On Divestiture Of Business
Net gain on divestiture of business.
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Statutory Federal Income Tax Rate
U.S. Federal Statutory Tax Rate
Common stock price per share
Shares Issued, Price Per Share
Energy Supply
Energy Supply [Text Block]
Energy supply.
Cybersecurity Risk Management Third Party Engaged [Flag]
Documents Incorporated by Reference [Text Block]
Documents Incorporated by Reference
Goodwill
Goodwill, Ending Balance
Goodwill, Beginning Balance
Goodwill, Total
Goodwill
Effective Income Tax Rate
Effective Income Tax Rate Reconciliation, Percent
Effective Income Tax Rate
Recoveries
Accounts Receivable, Allowance for Credit Loss, Recovery
Other Current Liabilities (current portion)
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]
Accrued Revenue
Total Accrued Revenue
Unbilled Contracts Receivable
Amounts Capitalized or Deferred
Defined Benefit Plan Capitalized And Deferred
Amounts of pension and other post retirement benefit costs capitalized and deferred.
Commitments And Contingencies [Table]
Commitments And Contingencies.
Geographical [Domain]
Geographical [Domain]
Income Tax, Examination [Table]
Other Noncurrent Assets:
Assets, Noncurrent [Abstract]
Shares Issued, Shares, Share-Based Payment Arrangement, Forfeited
Forfeited Shares
Public utilities approved increase amount of annual revenue to recover eligible capital investments
Public utilities approved increase amount of annual revenue to recover eligible capital investments
Public utilities approved increase amount of annual revenue to recover eligible capital investments
5.90% Notes, Due December 15, 2030
Senior Notes Five Point Nine Zero Percent Due December Fifteen Twenty Thirty [Member]
Senior Notes Five Point Nine Zero Percent Due December Fifteen Twenty Thirty [Member]
Environmental and Rate Case Costs and Other Expenditures
Environmental And Rate Case Costs And Other Expenditures [Member]
Environmental and Rate Case Costs and Other Expenditures [Member]
Common Shares [Table]
Common Shares [Table]
Allowance for doubtful accounts
Balance at Beginning of Period
Balance at End of Period
Accounts Receivable, Allowance for Credit Loss
Regulated Operation, Regulatory Liability [Table]
Investment Holdings Domain
Investment Holdings [Domain]
Divestiture of Non-Regulated Business Subsidiary
Divestitures Policy [Policy Text Block]
Divestitures Policy [Policy Text Block]
Benefits Paid
Defined Benefit Plan, Plan Assets, Benefits Paid
Summary of Significant Accounting Policies
Significant Accounting Policies [Text Block]
Regulatory Assets – Current
Less: Current Portion of Regulatory Assets
Regulatory Asset, Current
Finite-Lived Intangible Asset, Useful Life
Amortization period
Vesting [Domain]
Cybersecurity Risk Management, Strategy, and Governance [Table]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Reconciles Basic and Diluted Earnings Per Share
Dividends
Dividends [Policy Text Block]
Dividends.
Long Term Debt Amount Details [Axis]
Long term debt amount details.
Increase (Decrease) in Other Receivables
Exchange Gas Receivable
Restricted Stock Units Settled
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Settled In Period Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Settled In Period Weighted Average Grant Date Fair Value
Earnings Per Share, Basic, Total
Earnings Per Share, Basic
Earnings per Common Share - Basic
Repayment of Long-Term Debt
Long term debt repayments
Repayments of Long-Term Debt
Repayments of Long-Term Debt, Total
Equity Funds
Equity Funds
Equity Funds [Member]
Retirement Benefit Plans
Retirement Benefits [Text Block]
Environmental Remediation Expense, before Recovery, Statement of Income or Comprehensive Income [Extensible Enumeration]
Allowance for Doubtful Accounts
Allowances For Doubtful Accounts
Allowances for doubtful accounts text block.
Effective Income Tax Continuing Operations Amount
Effective Income Tax Continuing Operations Amount
Effective Income Tax Rate Amount
Northern Utilities And Fitchburg Member
Northern Utilities And Fitchburg
Northern Utilities And Fitchburg [Member]
Restricted Stock Units Granted
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fully Vested Grants In Period Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Fully Vested Grants in Period, Weighted Average Grant Date Fair Value.
Financial Instruments
Financial Instruments [Policy Text Block]
Financial instruments.
Interest and Other Income [Abstract]
Interest Income
Total Interest Expense, Net
Interest Expense, Net
Interest Income (Expense), Nonoperating
Revolving Credit Facility
Revolving Credit Facility [Member]
Retirement Plan Type [Domain]
Total Current Liabilities
Liabilities, Current
Regulatory Assets
Regulatory Assets—noncurrent
Regulatory Asset, Noncurrent
Period Type Axis
Period Type [Axis]
Estimated Percentage of Decoupled Sales That Are Subject To Revenue Decoupling [Table Text Block]
Estimated Percentage of Decoupled Sales That Are Subject To Revenue Decoupling [Table Text Block]
Estimated Percentage of Decoupled Sales
Accounts Receivable
Increase (Decrease) in Accounts Receivable
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities:
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]
Lessee, Operating Lease, Liability, to be Paid, Year Five
2030
Quarterly Payment [Member]
Quarterly payment.
Quarterly Payment
Subsegments [Axis]
Percentage Of Purchase Electric Supply
Percentage Of Purchase Electric Supply
Percentage Of Purchase Electric Supply
Receivables [Line Items]
Line items represent receivables.
Total Lease Obligations
Lease Obligation
Lease obligation.
First Mortgage Bonds 6.96% Senior Secured Notes, Due September 1, 2028
First Mortgage Bonds Six Point Nine Six Percent Senior Secured Notes Due September One Twenty Twenty Eight [Member]
First Mortgage Bonds Six Point Nine Six Percent Senior Secured Notes Due September One Twenty Twenty Eight [Member]
Future Operating Lease Payment Obligations and Future Minimum Lease Payments under Capital Leases
Schedule Of Future Minimum Payments For Obligations [Table Text Block]
Schedule Of Future Minimum Payments For Obligations [Table Text Block]
Long-Term Debt Issuance Costs
Payments of Debt Issuance Costs
Income Tax Examination [Line Items]
Consolidation Items [Domain]
Stockholders' Equity:
Equity, Attributable to Parent [Abstract]
Entity Small Business
Regulatory Defferals
Accounts Receivable Allowance For Credit Losses Provisions For Bad Debts Deferred Due To Regulatory Need
Accounts receivable allowance for credit losses provisions for bad debts deferred due to regulatory need.
Retained Earnings
Retained Earnings
Retained Earnings (Accumulated Deficit)
Retained Earnings (Accumulated Deficit), Total
Funded Status: Assets vs PBO
Defined Benefit Plan, Funded (Unfunded) Status of Plan
Defined Benefit Plan, Funded (Unfunded) Status of Plan, Total
Period Type Domain
Period Type [Domain]
Maine Natural Gas Corporation [Member]
Maine Natural Gas Corporation [Member]
Maine Natural Gas Corporation
Entity Well-known Seasoned Issuer
Entity Well-known Seasoned Issuer
Amount available for the payment of dividends
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments, Total
Proceeds from Issuance Initial Public Offering
Proceeds From Issuance Initial Public Offering
Sale of Stock, Price Per Share
Sale of stock, Average price per share
Subsequent Events
Subsequent Events, Policy [Policy Text Block]
Prepayments and Other related, current portion
Other Current Assets [Member]
Gas System Enhancement Recovery Cap Rate
Gas System Enhancement Recovery Cap Rate
Recovery cap rate
Dividends Paid
Payments of Dividends
Payments of Dividends, Total
Length Of Pipeline
Length Of Pipeline
Length of natural gas transmission pipeline.
Percentage of Weighted Average Cost Inventory
Percentage of Weighted Average Cost Inventory
Amendment Flag
Amendment
AFUDC and Other
Afudc And Other [Member]
Afudc and other.
Depreciation rate based on average depreciable property balance
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service
Product and Service [Domain]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount
U.S. Federal Statutory Tax Rate Amount
Health care cost trend rate determine plan costs
Health care cost trend rate determine plan costs
Regulatory Asset [Line Items]
LIABILITIES AND CAPITALIZATION:
Liabilities and Equity [Abstract]
Entity Address, Postal Zip Code
Cash Provided by Operating Activities
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation
Amount of Lease Obligation Finance Lease Liability
Amount of Lease Obligation Finance Lease Liability
Amount of Lease Obligations Recorded on Consolidated Balance Sheets
Amount of replacement investments approved by regulatory authority
Amount of replacement investments approved by regulatory authority
Amount of replacement investments approved by regulatory authority
Depreciation and Amortization
Utilities Operating Expense, Depreciation and Amortization
Depreciation & Amortization Expense
Common Stock
Common Stock [Member]
Cybersecurity Risk Role of Management [Text Block]
Total Operating Revenues
Regulated and Unregulated Operating Revenue
Regulated and Unregulated Operating Revenue, Total
Revenue Cap
Revenue Cap
Revenue Cap
Long-Term Debt, Maturity, Year One
Debt repayment, 2026
Lessee, Operating Lease, Liability, to be Paid, Year Three
2028
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total
Net Utility Plant, accumulated amortization
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance
Percentage of fully-vested restricted stock units that directors will receive in common shares when settled
Percentage Of Fully Vested Restricted Stock Units That Directors Will Receive In Common Shares When Settled
Percentage of fully-vested restricted stock units that Directors will receive in common shares when settled.
Massachusetts Solar Massachusetts Renewable Target Program (SMART) 3.0
Massachusetts Solar Massachusetts Renewable Target Program [Member]
Massachusetts Solar Massachusetts Renewable Target Program [Member]
Long-Term Renewable Contracts
Long-Term Renewable Contracts
Long-Term Renewable Contracts
Supplemental Employee Retirement Plans, Defined Benefit
Supplemental Employee Retirement Plans, Defined Benefit
Supplemental Employee Retirement Plan [Member]
Other Changes in Working Capital Items
Increase (Decrease) in Other Current Assets and Liabilities, Net
Long Term Debt Amount Details [Domain]
Long term debt amount details.
Entity Address, Address Line One
Total Deferred Tax Liabilities
Deferred Tax Liabilities, Gross
Gross Regulatory Liabilities
Percentage of approved return on equity
Public Utilities, Approved Return on Equity, Percentage
Fair Value Hierarchy and NAV [Axis]
Income Taxes
Income Tax, Policy [Policy Text Block]
Accruals For Environmental Loss Contingencies
Accruals For Environmental Loss Contingencies
Total Balance at Beginning of Period
Total Balance at end of Period
Pre sixty five retirees member.
Pre Sixty Five Retirees [Member]
Pre-65 retirees
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]
Supplemental Information:
Supplemental Cash Flow Information [Abstract]
Common
Public Utilities, Property, Plant and Equipment, Common
Construction Advances
Construction Advances
Construction Advances
Defined Benefit Plan, Expected Future Benefit Payment, Year Four
2029
Statement of Financial Position Location, Balance [Axis]
Investment Type [Axis]
Fair value of liabilities associated with fully vested RSUs that will be settled in cash
Fair Value Of Restricted Stock Units Settled In Cash
Fair Value of Restricted Stock Units to be settled in cash.
Operating Lease Right of Use Assets
Operating Lease, Right-of-Use Asset
Defined Benefit Plan, Plan Assets, Category [Domain]
Total Deferred Tax Assets
Deferred Tax Assets, Gross
Gross Regulatory Assets
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]
Retirement Benefits [Member]
Retirement Benefits [Member]
Retirement Benefits
Document Type
Document Type
Income Taxes Paid
Income Taxes Paid, Net
Income Taxes Paid, Net, Total
Collaborative Arrangement and Arrangement Other than Collaborative [Axis]
Residential
Residential [Member]
Residential
Collaborative Arrangement and Arrangement Other than Collaborative [Domain]
CIK
Entity Central Index Key
Line of Credit Facility [Table]
Retirement Benefit Obligations
Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent
Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent, Total
Restricted Stock Units Settled
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fully Vested Settled In Period Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Fully Vested Settled in Period, Weighted Average Grant Date Fair Value.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]
3.72% Senior Notes, Due November 1, 2027
3.72% Senior Notes, Due November 1, 2027
Senior Notes Three Point Seven Two Percent Due November One Twenty Twenty Seven [Member]
Senior Notes Three Point Seven Two Percent Due November One Twenty Twenty Seven [Member]
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation
Net Increase (Decrease) in Cash and Cash Equivalents
Subsequent Event Type [Domain]
Energy Supply Obligations
Energy Supply Obligations-Current
Energy Marketing Contract Liabilities, Current
Senior Notes Six Point Three One Percent Due Twenty Thirty Five [Member]
Senior Notes Six Point Three One Percent Due Twenty Thirty Five [Member]
6.31 % Senior Note Due to 2035
Weighted Average Non-Vested Restricted Shares Not Included in EPS Computation
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount
Plan Amendments
Defined Benefit Plan, Benefit Obligation, Increase (Decrease) for Plan Amendment
Credit Facility [Member]
Credit Facility Member
Credit Facility [Member]
First Mortgage Bonds 6.32% Senior Secured Notes, Due September 15, 2036
First Mortgage Bonds Six Point Three Two Percent Senior Secured Notes Due September Fifteen Twenty Thirty Six [Member]
First Mortgage Bonds Six Point Three Two Percent Senior Secured Notes Due September Fifteen Twenty Thirty Six [Member]
Common Stock, Par or Stated Value Per Share
Common stock per value
Liquefied Natural Gas & Other
Natural Gas Liquids (NGL) [Member]
Regulatory Accounting
Public Utilities, Policy [Policy Text Block]
2.64% Senior Notes, Due December 18, 2030
Senior Notes Two Point Six Four Percent Due December Eighteen Twenty Thirty [Member]
Senior notes two point six four percent due december eighteen twenty thirty.
Base Rate [Member]
Senior Notes Five Point Seven Four Percent Due Twenty Thirty Nine [Member]
Senior Notes Five Point Seven Four Percent Due Twenty Thirty Nine [Member]
5.74% Senior Note Due to 2039
Dividend and Distribution Reinvestment and Share Purchase Plan
Dividend And Distribution Reinvestment And Share Purchase Plan [Member]
Dividend and Distribution Reinvestment and Share Purchase Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Document Financial Statement Error Correction [Flag]
Document Financial Statement Error Correction [Flag]
Components of Retirement Plan Costs
Schedule of Costs of Retirement Plans [Table Text Block]
Debt Disclosure [Abstract]
7.72% Senior Notes, Due December 3, 2038
Senior Notes Seven Point Seven Two Percent Due December Three Twenty Thirty Eight [Member]
Senior Notes Seven Point Seven Two Percent Due December Three Twenty Thirty Eight [Member]
Equity [Table]
Equity [Table]
State and Local Income Tax Expense (Benefit), Continuing Operations
State and Local Income Tax Expense (Benefit), Continuing Operations, Total
State Income Taxes
Recovered over the next seven years
Debt Instrument, Redemption, Period Five [Member]
Contractual Obligation Fiscal Year Maturity Schedule Line Items
Contractual Obligation Fiscal Year Maturity Schedule [Line Items]
Electric
Public Utilities, Property, Plant and Equipment, Transmission and Distribution
Public Utilities, Property, Plant and Equipment, Transmission and Distribution, Total
Current Fiscal Year End Date
Actual Return on Plan Assets
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)
Fitchburg Gas Company
Fitchburg Gas Company [Member]
Fitchburg gas company
Increase (decrease) in capital lease obligations.
Increase Decrease In Capital Lease Obligations
Increase in Capital Lease Obligations
Regulatory Liability [Domain]
Dividend Equivalents Earned
Share Based Payment Award Equity Instruments Other Than Options Dividend Equivalent Rights In Period
Share Based Payment Award Equity Instruments Other Than Options Dividend Equivalent Rights In Period.
Gas Segment
Gas Segment [Member]
Gas Segment [Member]
Carrying costs
Additional Carrying Costs
Additional Carrying Costs
Entity Address, State or Province
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Shares Issued
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Shares Issued
Shares Issued
5.70 % Senior Note Due to July 2, 2033
Senior Notes Five Point Seven Zero Percent Due july Two Twenty Thirty Three Member
Senior Notes Five Point Seven Zero Percent Due july Two Twenty Thirty Three Member
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number
Restricted Shares as of December 31, 2025
Restricted Shares as of December 31, 2024
Cost Of Operating Revenue
Other Cost of Operating Revenue
Available revolving credit facility
Line of Credit Facility, Remaining Borrowing Capacity
Proceeds from (Repayments of) Short-Term Debt
Proceeds from (Repayments of) Short-Term Debt, Total
Proceeds (Repayment of) from Short-Term Debt, net
Regulatory Liabilities Abstract
Regulatory Liabilities [Abstract]
Components of Exchange Gas Receivable
Schedule Of Other Accounts Receivable [Table Text Block]
Description of the components and amounts included in Exchange Gas Receivable.
Preferred stock, outstanding
Preferred Stock, Shares Outstanding
Preferred Stock, Shares Outstanding, Beginning Balance
Preferred Stock, Shares Outstanding, Ending Balance
Capital lease
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations
Defined Benefit Plan, Assumptions [Table Text Block]
Inventory [Axis]
Geographical [Axis]
Geographical [Axis]
Facility power capacity to be procured in the future
Facility Power Capacity To Be Procured In The Future
Facility power capacity to be procured in the future.
Accounts Receivable
Accounts Receivable [Member]
Petroleum Reserves [Axis]
Working Capital
Working Capital
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share Line Items
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount
State Income Taxes, net of Federal Income Tax Amount
Finance Lease, Liability, to be Paid, after Year Five
2031-2035
Exchange Gas Obligation [Policy Text Block]
Exchange Gas Obligation [Policy Text Block]
Exchange Gas Obligation
Deferred Tax Assets and Liabilities
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]
Interest and Other Income
Interest Income
Interest and Other Income
Interest Income
Performance Shares [Member]
Performance Restricted Shares
Accumulated deferred income taxes
Increase (Decrease) in Deferred Income Taxes
Accumulated deferred income taxes
Other Postretirement Benefit Plans, Defined Benefit
Other Postretirement Benefits Plan [Member]
Retirement Benefits
Estimated Fair Value of Long-Term Debt
Long-Term Debt, Fair Value
Subsequent Event
Subsequent Event [Member]
ISO-NE Obligations
New England [Member]
New England [Member]
Arrearage Management Program [Member]
Arrearage Management Program [Member]
Arrearage Management Program
Regulatory Assets Deferred Costs
Regulatory Assets Deferred Costs
Regulatory assets deferred cost
Investments in Marketable Securities
Marketable Securities, Policy [Policy Text Block]
Restricted Stocks [Table]
Restricted Stocks [Table]
Other Assets
Other Assets, Noncurrent
Termination agreements
Gain (Loss) on Contract Termination
Gas Division [Member]
Gas Division [Member]
Antidilutive Securities [Axis]
Restricted stock vesting percentage annually
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage
Contractual Obligation, to be Paid, after Year Five
2030 & Beyond
2031 & Beyond
Other Subsegments [Member]
Other Subsegments [Member]
Customer [Domain]
Estimate program cost
Estimated Program Cost
Estimated Program Cost
Natural gas, underground storage
Natural Gas Pipeline Capacity Per Day
Natural gas pipeline, capacity per day.
Preferred Stock
Preferred Stock, Value, Issued
Components Of Accrued Revenue Abstract
Components of Accrued Revenue [Abstract]
Massachusetts And Maine [Member]
Massachusetts And Maine [Member]
Massachusetts and maine.
6.79% Senior Notes, Due October 15, 2025
Senior Notes Six Point Seven Nine Percent Due October Fifteen Twenty Twenty Five [Member]
Senior Notes Six Point Seven Nine Percent Due October Fifteen Twenty Twenty Five [Member]
Long-term debt, maturity date
Debt instrument due date
Debt Instrument, Maturity Date
GSEP Two Thousand Twenty Five [Member]
GSEP Two Thousand Twenty Five [Member]
GSEP Two Thousand Twenty Five
Minimum
Minimum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value
Weighted Average Stock Price Granted
Unitil Corporation
Unitil Corporation [Member]
Unitil corporation.
Current Assets:
Assets, Current [Abstract]
Electric Division [Member]
Electric Division [Member]
Track One [Member]
Track One [Member]
Regulatory Assets and Liabilities Disclosure [Abstract]
Fair Value Inputs Level 3
Fair Value, Inputs, Level 3 [Member]
Segment Reporting [Abstract]
Utility Plant Differences
Deferred Tax Liabilities, Property, Plant and Equipment
Total Capitalization
Capitalization, Long-Term Debt and Equity
Noncurrent Balance at End of Period
Environmental Obligations
Accrued Environmental Loss Contingencies, Noncurrent
Tax Period [Domain]
Current Liabilities:
Liabilities, Current [Abstract]
Dividend Equivalents Earned
Share Based Payment Award Equity Instruments Other Than Options Fully Vested Dividend Equivalent Rights In Period Weighted Average Grant Date Fair Value
Share Based Payment Award Equity Instruments Other Than Options Fully Vested Dividend Equivalent Rights In Period Weighted Average Grant Date Fair Value.
Regulatory Asset [Axis]
GSEP Two Thousand Twenty Six [Member]
GSEP Two Thousand Twenty Six [Member]
GSEP Two Thousand Twenty Six
Derivative Assets [Member]
Derivative Assets [Member]
Derivative Assets
Imputed Interest On Capital Leases
Imputed Interest On Capital Leases
Less: Interest
Accounts Receivable, Net
Accounts Receivable, after Allowance for Credit Loss, Current
Accounts Receivable, after Allowance for Credit Loss, Current, Total
Interest Expense
Interest Expense, Operating and Nonoperating [Abstract]
Regulatory Liabilities
Less: Current Portion of Regulatory Liabilities
Regulatory Liability, Current
Repurchase expense
Stock Repurchase Program Fees And Expenses Related To Tender Offer
Stock repurchase program fees and expenses related to tender offer.
7.37% Senior Notes, Due January 15, 2029
Senior Notes Seven Point Three Seven Percent Due January Fifteen Twenty Twenty Nine [Member]
Senior Notes Seven Point Three Seven Percent Due January Fifteen Twenty Twenty Nine [Member]
Commitments and Contingencies (Note 7)
Commitments and Contingencies
MAINE
Provision for income taxes
Disposal Group Including Discontinued Operations Tax Effect Of Gain On Divestiture
Disposal Group Including Discontinued Operations Tax Effect Of Gain On Divestiture
Leases
Lessee, Leases [Policy Text Block]
Service Cost
Service Cost
Defined Benefit Plan, Service Cost
Weighted Average Stock Price as of December 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
Weighted Average Stock Price as of December 31, 2025
Provision for Bad Debt
Provision
Accounts Receivable, Credit Loss Expense (Reversal)
Total Operating Lease Obligations
Total Operating Lease Obligations
Amount of Lease Obligations Recorded on Consolidated Balance Sheets
Operating Lease, Liability
Remediation costs
Remediation costs
Remediation costs
Auditor Firm ID
Auditor Firm ID
Credit facility, daily fluctuating rate of interest
Debt Instrument, Basis Spread on Variable Rate
Dividend rate
Preferred Stock, Dividend Rate, Percentage
Scenario Forecast
Forecast [Member]
Short-Term Debt
Short-Term Borrowings Outstanding
Short-Term Debt
Short-Term Debt, Total
Purchase commitments for data sharing platform investments
Purchase commitments for data sharing platform investments
Purchase commitments for data sharing platform investments
Materials and Supplies
Inventory, Raw Materials and Supplies, Gross
Inventory, Raw Materials and Supplies, Gross, Total
Exchange Gas Obligation
Obligations [Member]
Concentration Risk Benchmark [Axis]
Concentration Risk Benchmark [Axis]
Unitil Reality Corp
Unitil Reality Corp [Member]
Unitil Reality Corp[Member]
Classification of the Company Lease Obligations
Schedule Of Capital Leases Obligations [Table Text Block]
Schedule of Capital Leases Obligations [Table Text Block]
Financing Receivable, Impaired [Line Items]
Issuance of long-term debt
Debt Issuance Costs, Noncurrent, Net
Debt Issuance Costs, Noncurrent, Net, Total
Long-Term Debt, Maturity, Year Two
Debt repayment, 2027
New Hampshire Customers [Member]
New Hampshire Customers [Member]
Storm Cost Deferral Petition [Member]
Storm Cost Deferral Petition [Member]
Income Taxes Paid Net Of Refunds [Table]
Income Taxes Paid Net Of Refunds Table
Other Current Liabilities (current portion)
Finance Lease, Liability, Current
Other Current Liabilities (current portion)
Recover costs of repairing damage
Contract with Customer, Right to Recover Product
Contract with Customer, Right to Recover Product, Total
Percentage of power supply requirement
Power Supply Cost Benefit Variance Percentage
Power supply cost benefit variance percentage.
Noncurrent Liabilities:
Liabilities, Noncurrent [Abstract]
Text Block [Abstract]
Other
Other Funds [Member]
Other Funds [Member]
Senior Notes Five Point Five Four Percent Due Twenty Thirty Four [Member]
Senior Notes Five Point Five Four Percent Due Twenty Thirty Four [Member]
5.54% Senior Note Due to 2034
Capital Expenditures Included in Accounts Payable
Capital Expenditures Incurred but Not yet Paid
Reduction in total residential sector budget
Reduction in Total Residential Sector Budget
Reduction in Total Residential Sector Budget
Net Income
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total
Assets under Capital Leases [Member]
Assets Held under Capital Leases [Member]
Other, net
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item
Amount of Regulatory Costs Not yet Approved
Regulatory assets approved recovery amount
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]
Weighted Average Number of Shares Outstanding, Basic
Weighted Average Number of Shares Outstanding, Basic, Total
Weighted Average Common Shares Outstanding - Basic
Weighted average number of shares outstanding used in the calculation of basic earnings per share
Scenario [Axis]
Environmental Obligations Recognized by Company
Schedule of Environmental Loss Contingencies by Site [Table Text Block]
Document Information:
Document Information [Line Items]
Regulatory assets
Regulatory Asset
Regulatory Asset, Total
Total Regulatory Assets
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount
Other Amount
Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]
Public Utilities, Inventory [Line Items]
Segments [Axis]
Transfer revenue amount
Increase Decrease Transfer Revenue Amount
Increase Decrease Transfer Revenue Amount
Long-Lived Tangible Asset [Domain]
Additions
Accrual for Environmental Loss Contingencies, Charges to Expense for New Losses
3.43% Senior Notes, Due December 18, 2029
3.43% Senior Notes, Due December 18, 2029
Senior Unsecured Notes Three Point Four Three Percent Due December Eighteen Twenty Twenty Nine [Member]
Senior Unsecured Notes Three Point Four Three Percent Due December Eighteen Twenty Twenty Nine [Member]
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]
Unbilled Revenues
Unbilled Revenues
Unbilled Revenues [Member]
Investment Holdings Axis
Investment Holdings [Axis]
Effective Income Tax Rate Reconciliation, Tax Credit, Percent
Effective Income Tax Rate Reconciliation, Tax Credit, Percent, Total
Production Tax Credit Rate
Production Tax Credit Rate
Long-Term Debt
Long-Term Debt
Total [Member]
Total [Member]
Total
Variable Rate [Domain]
Actuarial (Gain) or Loss
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)
Vesting Annually
Vesting Annual [Member]
Vesting Annual [Member]
Total Stockholders' Equity
Equity, Attributable to Parent
Beginning Balance
Ending Balance
Summary of Interest Expense and Interest Income
Interest Income and Interest Expense Disclosure [Table Text Block]
Energy Member
Energy Commodity
Energy [Member]
Average Interest Rate On Debt
Average interest rate on debt.
Average Interest Rate On Debt
Marketing And Outreach [Member]
Marketing And Outreach [Member]
Type of Restructuring [Domain]
Effective income tax rate reconciliation domestic income tax rate differential.
Effective Income Tax Rate Reconciliation Domestic Income Tax Rate Differential
Utility Plant Differences
Use of Estimates
Use of Estimates, Policy [Policy Text Block]
Second Solicitation Member
Second Solicitation [Member]
Fixed Income Securities
Fixed Income Securities [Member]
Long-Term Debt, Maturity, Year Five
Debt repayment, 2030
Track Two [Member]
Track Two [Member]
4.04% Senior Notes, Due September 12, 2049
Senior Notes Four Point Zero Four Percent Due September Twelve Twenty Forty Nine [Member]
Senior Notes Four Point Zero Four Percent Due September Twelve Twenty Forty Nine Member.
Federal, State, and Local, Income Tax Expense (Benefit), Continuing Operations
Federal, State, and Local, Income Tax Expense (Benefit), Continuing Operations, Total
Total Cash Paid for Income Taxes, net of Refunds
Defined Benefit Plan Disclosure [Line Items]
Over-Allotment Option [Member]
5.54% Senior Notes Due to August 21, 2034
Senior Notes Five Point Five Four Percent Due August Twenty One Twenty Thirty Four [Member]
Senior Notes Five Point Five Four Percent Due August One Twenty Twenty Thirty Four [Member]
Bangor Natural Gas [Member]
Bangor Natural Gas
Bangor Natural Gas
Divestiture [Member]
Divestiture [Member]
Power Supply Contract Divestitures
Environmental Matters
Environmental Matters [Member]
Environmental Matters [Member]
Fair Value Of Plan Assets Member
Fair Value Of Plan Assets
Fair Value Of Plan Assets [Member]
Debt Instrument, Name [Domain]
Regulatory Asset [Domain]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share Table
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Table]
Long-Term Debt, Maturity, Year Four
Debt repayment, 2029
Prepayments and Other
Prepaid Expense and Other Assets
Net Interest Income [Line Items]
Net Interest Income [Line Items]
Net interest income.
Pension expense
Pension Cost (Reversal of Cost)
Mayflower Wind energy [Member]
Mayflower Wind energy
Number of Customer
Number of Customer
Number of Customer
Operating Revenue
Operating Revenue
Operating Revenue
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Energy Supply Costs
Energy Supply Costs
Energy Supply Costs
Segment Reporting, Other Segment Item, Amount
Other Segment Expenses (Income)
Less: Interest
Imputed Interest On Operating Leases
Imputed Interest On Operating Leases.
Regulatory Liability
Regulatory Liability
Regulatory Liability, Total
Total Regulatory Liabilities
Gas Ratepayers
Gas Rate Payers [Member]
utl:GasRatePayersMember
Order [Axis]
Order [Axis]
Renewable Energy Portfolio Standards [Policy Text Block]
Renewable Energy Portfolio Standards [Policy Text Block]
Renewable Energy Portfolio Standards
Subtotal Interest Expense
Interest Expense
Interest Expense, Operating and Nonoperating
Exchange Gas Receivable
Receivable [Policy Text Block]
Mutual Fund
Mutual Fund [Member]
All Entities
Entity [Domain]
Transition Services Agreement Cost
Transition Services Agreement Cost
Transition Services Agreement Cost
Credit Facility [Axis]
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block]
Granite State Gas Transmission Inc
Granite State Gas Transmission Inc
Granite State Gas Transmission Inc [Member]
Granite State Gas Transmission Inc [Member]
State
Current State and Local Tax Expense (Benefit)
Estimated Future Benefit Payments
Schedule of Expected Benefit Payments [Table Text Block]
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]
Finance Lease, Liability, to be Paid, Year One
2026
Energy Storage Systems 1
Energy Storage Systems 1
Energy storage systems
Tax Period [Axis]
Other Assets related, noncurrent portion
Other Noncurrent Assets [Member]
Deferred Tax and Other Liabilities, Noncurrent
Deferred Income Taxes, Net
Operating Lease Obligations:
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
Power supply contract duration
Power Supply Agreement
Power supply agreement.
Gas
Public Utilities Property Plant And Equipment Gas
Public Utilities Property Plant and Equipment related to Gas Operations.
Regulatory Assets
Regulatory Assets
Regulatory Asset [Member]
Regulatory Asset [Member]
Acquisition of Aquarion Water Companies Policy Text Block
Acquisition of Aquarion Water Companies Policy Text Block
Acquisition of Aquarion Water Companies
Pension Plans
Pension Plan [Member]
Northern Utilities Inc
Northern Utilities Inc [Member]
Northern Utilities Inc [Member]
Utility Plant
Property, Plant and Equipment, Policy [Policy Text Block]
Four Zero One K Plan
Four Zero One K Plan [Member]
Four Zero One K Plan Member
Entity Address, City or Town
Health Care Cost Trend Rate, Description
Health Care Cost Trend Rate, Description
Billing Status, Type [Axis]
Billing Status, Type [Axis]
Number of Reportable Segments
Number of reportable segments
Restricted Stock Units Granted
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Grants In Period Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Grants In Period Weighted Average Grant Date Fair Value
Security Exchange Name
Credit Facility [Domain]
Total Long-Term Debt
Long-Term Debt, Gross
Mutual Fund Including Cash And Cash Equivalents Member
Mutual Fund Including Cash And Cash Equivalents
Mutual Fund Including Cash And Cash Equivalents [Member]
Income Before Income Taxes
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest
Common Equity
Common Stock Including Additional Paid in Capital [Member]
Percentage of approved return on equity, reflecting on debt
Public Utilities, Approved Debt Capital Structure, Percentage
Finance Lease, Liability, to be Paid, Year Five
2030
3.78% Senior Notes, Due September 15, 2040
Senior Notes Three Point Seven Eight Percent Due September Fifteen Twenty Forty [Member]
Senior Notes Three Point Seven Eight Percent Due September Fifteen Twenty Forty Member.
Senior Notes Five Point Nine Nine Percent Due Twenty Forty Four [Member]
5.99% Senior Note Due to 2044
Senior Notes Five Point Nine Nine Percent Due Twenty Forty Four [Member]
Antidilutive Securities, Name [Domain]
Increase or decrease of Net Periodic Benefit Cost (NPBC) due to change in the discount rate
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Increase (Decrease) for Plan Amendment
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Income Taxes
Income Taxes [Member]
Income Taxes [Member]
Gain on divestiture of business, pretax
Gain On Divestiture Of Business Pretax
Gain on divestiture of business pretax.
Interest Paid
Interest Paid, Excluding Capitalized Interest, Operating Activity
Range [Domain]
Statistical Measurement [Domain]
4.42% Senior Notes, Due October 15, 2044
Senior Notes Four Point Four Two Percent Due October Fifteen Twenty Forty Four [Member]
Senior Notes Four Point Four Two Percent Due October Fifteen Twenty Forty Four [Member]
Order Flow Fees
Order providing cost
Contractual Obligation, Fiscal Year Maturity [Abstract]
Total Current Assets
Assets, Current
Period End Date
Document Period End Date
Cash Deposits
Cash Deposits
Cash Deposits
Fair Value Hierarchy and NAV [Domain]
ICFR Auditor Attestation Flag
ICFR Auditor Attestation Flag
Benefits Paid
Defined Benefit Plan, Benefit Obligation, Benefits Paid
Benefits Paid
Natural Gas
Public Utilities, Inventory, Natural Gas [Member]
Common stock shares repurchase
Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Purchased for Award
Senior Notes Five Point Seven Zero Percent Due Twenty Thirty [Member]
Senior Notes Five Point Seven Zero Percent Due Twenty Thirty [Member]
5.70 % Senior Note Due to 2030
Other Noncurrent Liabilities (long-term portion)
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]
Fitchburg Customers [Member]
Fitchburg Customers [Member]
Operating Lease Obligations (current portion)
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]
Hardship accounts in regulatory assets
Hardship Accounts in Regulatory Assets
Hardship accounts in regulatory assets.
Description of variable rate basis
Debt Instrument, Description of Variable Rate Basis
Statement of Financial Position [Abstract]
Restricted Stock Units (RSUs)
Restricted Stock Units (RSUs) [Member]
Loss Contingency Nature [Axis]
Net Interest Income Table
Net Interest Income [Table]
Sub-total
Defined Benefit Plan Gross Periodic Benefit Cost
The gross amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).
Other Operating Revenue - Non-regulated
Revenue [Policy Text Block]
Loss Contingency, Nature [Domain]
Antidilutive Security, Excluded EPS Calculation [Table]
Vesting [Axis]
Program costs
Program Costs
Program Costs
Utilities [Member]
Utilities [Member]
Utilities
Net Operating Loss Carryforwards Utilized For Income Taxes
Net Operating Loss Carryforwards Utilized For Income Taxes
Net operating loss carryforwards utilized for income taxes.
Class of Stock [Axis]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net Deferred Tax Liabilities
Deferred Tax Liabilities, Net
Participant Contributions
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Propane
Propane [Member]
Weighted average interest rate on short term borrowings
Short-Term Debt, Weighted Average Interest Rate, at Point in Time
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
DebtInstrumentVariableInterestRateAdditionalSpread
DebtInstrumentVariableInterestRateAdditionalSpread
Debt instrument variable interest rate additional spread
Regulatory Assets
Schedule of Regulatory Assets [Table Text Block]
Senior Notes Five Point Seven Zero Percent Due July Eight Twenty Thirty [Member]
Senior Notes Five Point Seven Zero Percent Due July Eight Twenty Thirty [Member]
5.70% Senior Notes, Due July 8, 2030
Energy [Domain]
Contractual Obligation, to be Paid, Year Two
2024
2027
Components of Energy Supply Obligations
Supply Commitment [Table Text Block]
Cost of Removal Obligations
Cost of removal obligation
Asset Retirement Obligations, Noncurrent
Asset Retirement Obligations, Noncurrent, Total
Expected Return on Plan Assets
Defined Benefit Plan, Expected Return (Loss) on Plan Assets
Lessee, Operating Lease, Liability, to be Paid, Year Two
2027
Materials And Supplies [Member]
Materials and supplies.
Materials And Supplies
Other
Other Regulatory Assets (Liabilities) [Member]
Fitchburg Manufactured Gas Plant Site [Member]
Fitchburg Manufactured Gas Plant Site [Member]
Fitchburg Manufactured Gas Plant Site
Common Stock Offering Price
Common Stock Offering Price
Common stock offering price
Restricted Stock
Restricted Stock [Member]
Deferred Revenue Arrangement, by Type [Table]
Variable Rate [Axis]
Weighted Average Number of Shares Outstanding, Diluted
Weighted Average Number of Shares Outstanding, Diluted, Total
Weighted Average Common Shares Outstanding - Diluted
Adjusted weighted average number of shares outstanding used in the calculation of diluted earnings per common share
Environmental Exit Cost [Table]
Entity File Number
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent
Other Rate
Cover
Cover [Abstract]
Deferred Income Tax Provision
Deferred Federal, State and Local, Tax Expense (Benefit) [Abstract]
Fair Value of Long Term Debt
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]
Total funded indebtedness as percentage of capitalization
Percentage Of Indebtedness To Net Capital
Percentage Of Indebtedness To Net Capital.
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period
Forfeited under the stock plan
Forfeited
Taxes Payable
Taxes Payable, Current
Taxes Payable, Current, Total
Payments on Capital Leases
Lease Obligation Incurred
Environmental Restoration Costs [Member]
Investments [Domain]
Real Estate Funds
Real Estate Funds [Member]
Billed and Unbilled Revenue
Billed And Unbilled Revenue [Member]
Billed and unbilled revenue.
Scenario [Domain]
Senior Unsecured Notes Five Point Nine Nine Percent Due August Twenty One, Twenty Thirty Four [Member]
Senior Unsecured Notes Five Point Nine Nine Percent Due August Twenty One, Twenty Thirty Four [Member]
5.99% Senior Notes, Due August 21, 2034
Number of Subsidiaries
Number of Subsidiaries.
Number of Subsidiaries
Deferred Tax Liabilities, Regulatory Assets and Liabilities
Regulatory Assets and Liabilities
Restricted stock available for awards
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized
Number of Operating Segments
Number of operating segments
Sale of Stock [Domain]
Segment Information
Segment Reporting Disclosure [Text Block]
First Mortgage Bonds 3.58% Senior Secured Notes Due September 15, 2040
First Mortgage Bonds Three Point Fifty Eight Percent Senior Secured Notes Due September Fifteen Twenty Forty [Member]
First Mortgage Bonds Three Point Fifty Eight Percent Senior Secured Notes Due September Fifteen Twenty Forty Member
Tax Jurisdiction of Domicile [Extensible Enumeration]
Total Gas and Electric Operating Revenues
Revenue from Contract with Customer, Including Assessed Tax
Deferred Tax Assets Regulatory Assets
Deferred Tax Assets Regulatory Assets
Regulatory Assets and Liabilities
Other, net
Deferred Tax Assets, Other
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Settled
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Settled
Restricted Stock Units Settled
Income Taxes [Line Items]
Income Taxes [Line Items]
Current Income Tax Provision
Current Federal, State and Local, Tax Expense (Benefit) [Abstract]
Less: Accumulated Depreciation
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation
Components of Accrued Revenue
Unbilled Accounts Receivable [Table Text Block]
Description of the components and amounts included in Accrued Revenue.
Senior Notes Six Point Three One Percent Due July Eight Twenty Thirty Five [Member]
Senior Notes Six Point Three One Percent Due July Eight Twenty Thirty Five [Member]
6.31% Senior Notes, Due July 8, 2035
Senior Notes Five Point Nine Nine Percent Due Twenty Thirty Four [Member]
Senior Notes Five Point Nine Nine Percent Due Twenty Thirty Four [Member]
5.99% Senior Note Due to 2034
Recently Issued Pronouncements
New Accounting Pronouncements, Policy [Policy Text Block]
Nature of Operations
Nature Of Operations [Policy Text Block]
It represents Nature Of Operations Policy
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Restricted stock vesting period
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period
Business Combination, Recognized Liability Assumed, Liability
Business Combination, Recognized Liability Assumed, Liability, Total
Business Acquisition Liabilities Assumed
Percentage of approved return on equity, reflecting on equity
Public Utilities, Approved Equity Capital Structure, Percentage
Accrued Revenue
Increase (Decrease) in Contract with Customer, Asset
Ultimate Health Care Cost Trend Rate
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate
Health care cost trend rate, ultimate rate
Issuance of Long-Term Debt
Proceeds from Issuance of Long-Term Debt
Proceeds from Issuance of Long-Term Debt, Total
Exchange Gas Receivable
Total Exchange Gas Receivable
Other Receivables, Net, Current
Other Receivables, Net, Current, Total
Lease term
Lessee, Operating Lease, Term of Contract
Actual Allocation
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage
Common Equity Outstanding
Common Stock, Shares, Outstanding
Shares as of December 31, 2024
Shares as of December 31, 2025
Other Current Liabilities (current portion)
Operating Lease, Liability, Current
Operating Lease Obligations
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Weighted Average Grant Date Fair Value
Beginning Liability Weighted Average Stock Price
Gas And Electric Supply Contractual Obligations
Contractual Obligation, Fiscal Year Maturity [Table Text Block]
Prior Service Cost Amortization
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Cybersecurity Risk Management Processes Integrated [Flag]
Document Transition Report
Time Restricted [Member]
Time Restricted [Member]
Time Restricted
Third Amendment Credit Facility Member [Member]
Third Amendment Credit Facility Member [Member]
Third Amendment Credit Facility Member [Member]
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description
Defined benefit plan, assumed health care cost trend rate, description
Income Taxes Paid Net Of Refunds [Line Items]
Income Taxes Paid Net Of Refunds Line Items
Fair Value Of Marketable Securities Abstract
Fair Value of Marketable Securities [Abstract]
Provisions for Federal and State Income Taxes
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]
Retirement Benefit Obligations
Pension and Other Postretirement Plans, Nonpension Benefits, Policy [Policy Text Block]
Statement of Cash Flows [Abstract]
Oil and Gas [Policy Text Block]
Acquisition of Bangor Natural Gas Company
Program [Domain]
Program [Domain]
Weighted-Average Stock Price
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
C&I
Commercial And Industrial [Member]
Commercial and industrial
Federal
Current Federal Tax Expense (Benefit)
Issuance of Common Shares
Stock Issued During Period, Value, New Issues
Income Taxes Paid Net of Refunds
Schedule of Income Tax Paid Net Of Refunds [Table Text Block]
Schedule of Income Tax Paid Net Of Refunds Table Text Block
Table Text Block Supplement [Abstract]
Maine Natural
Maine Natural [Member]
Maine Natural [Member]
Payments to Acquire Businesses, Net of Cash Acquired
Payments to Acquire Businesses, Net of Cash Acquired, Total
Acquisition, Net of Cash Acquired
Acquisitions, Net of Cash Acquired
Equity [Text Block]
Equity
Accounts and Financing Receivables [Table]
Offshore Energy Member
Offshore Wind Energy
Offshore Energy [Member]
Share based compensation expense
Restricted Stock or Unit Expense
Share-Based Compensation Arrangement by Share-Based Payment Liability Instruments Other than Options, Grants in Period
Share-Based Compensation Arrangement by Share-Based Payment Liability Instruments Other than Options, Grants in Period
Restricted Stock Units Granted
Cash And Cash Equivalents Acquired
Cash And Cash Equivalents Acquired
Cash And Cash Equivalents Acquired
Restricted Shares Issued in Conjunction with Stock Plan
Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]
Other, net
Deferred Tax Liabilities, Other
Cybersecurity Risk Management Processes Integrated [Text Block]
Sale of Stock, Consideration Received Per Transaction
Gross proceeds
Net Income
Net Income Applicable to Common Shares
Public Infrastructure Offering [Member]
Public Infrastructure Offering [Member]
Operating Lease, Cost
Total rental expense under operating leases
Line of Credit Facility [Line Items]
Line of Credit Facility [Line Items]
Benefit Obligation
Benefit Obligation [Member]
Benefit Obligation Member
Operating lease obligations
Operating Lease, Payments
Derivatives, Fair Value [Line Items]
Natural gas storage inventory
Energy Related Inventory, Natural Gas in Storage
Assets [Abstract]
Period 1
Period One [Member]
Period one member.
Before June 1, 2022
Business Combination, Price of Acquisition, Expected
Document Fiscal Year Focus
Exercise Price Range [Domain]
Concentration Risk Benchmark [Domain]
Concentration Risk Benchmark [Domain]
Investing Activities:
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Retirement Benefits [Abstract]
Accounts Payable
Accounts Payable, Current
Accounts Payable, Current, Total
Interest On Longterm Debt Member
Interest on Long-Term Debt [Member]
Interest on LongTerm Debt [Member]
Long-Term Debt
Interest Expense, Long-Term Debt
Interest Expense, Long-Term Debt, Total
Other Operating Segment [Member]
Other
Participant Contributions
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant
Federal
Deferred Federal Income Tax Expense (Benefit)
Contractual Obligation, to be Paid, Year Four
2026
2029
Shares Issued Under Stock Plans
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture, Total
Share Based Payment Liability Instruments Other Than Options Dividend Equivalent Rights In Period
Share Based Payment Liability Instruments Other Than Options Dividend Equivalent Rights In Period
Dividend Equivalents Earned
Operating Revenues Abstract
Operating Revenues [Abstract]
Gas and Oil Acreage [Line Items]
Oil and Gas, Acreage [Line Items]
Fair Value
Fair Value Measurement, Policy [Policy Text Block]
Restricted Stock Units Issued
Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block]
Regulatory Amortization of Excess ADIT
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Percent
Rate Adjustment Mechanism Revenue
Rate Adjustment Mechanism Revenue [Member]
Rate adjustment mechanism revenue.
Receivables Table
Receivables [Table]
Approved annual increase in rates
Public Utilities, Approved Rate Increase (Decrease), Amount
Average Participating Securities
Average Participating Securities
Less average participating securities
Commitments and Contingencies Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, Tax Credit, Amount
Effective Income Tax Rate Reconciliation, Tax Credit, Amount, Total
Production Tax Credit Amount
Production Tax Credit
Lessee, Operating Lease, Liability, to be Paid, Year One
2026
Fitchburg Performance Base Rate Adjustment Gas [Member]
Fitchburg Performance Base Rate Adjustment Gas [Member]
Fitchburg Performance Base Rate Adjustment Gas
Restricted Stock Units
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Sale of Stock, Consideration Received on Transaction
Net Proceeds
Segment Profit (Loss)
Net Income (Loss) Available to Common Stockholders, Basic
Net Income (Loss) Available to Common Stockholders, Basic, Total
Net Income Attributable to Commons Shares
Regulatory assets approved increase in revenue due to be recovered
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided
Remuneration Percentage
Remuneration Percentage
Remuneration percentage.
Equity Issuance [Member]
Equity Issuance [Member]
Equity Issuance
Debt Instrument [Axis]
Regulatory Liabilities
Regulatory Liability Interest Expense
Regulatory liability interest expense.
Energy Supply Abstract
Energy Supply [Abstract]
Total Common Stock Equity
Beginning Balance
Ending Balance
Common Stock Equity
Common Stock Equity
Lessee, Operating Lease, Liability, to be Paid, after Year Five
2031-2035
Interest Cost
Interest Cost
Defined Benefit Plan, Interest Cost
State Taxes Credit to Offset Future Taxes
State Taxes Credit to Offset Future Taxes
State Taxes Credit to Offset Future Taxes
Period 3
Period Three [Member]
Period Three Member.
After August 1, 2022
Regulatory Assets Total Approved Recovery Amount
Regulatory Assets Total Approved Recovery Amount
Regulatory recovery amount
Sale of Stock [Axis]
Derivatives
Derivatives, Policy [Policy Text Block]
Defined Benefit Plan, Expected Future Benefit Payment, Year One
2026
Employer Contributions, Participant Contributions and Benefit Payments
Schedule Of Contributions Defined Benefit Pension And Other Postretirement Plan [Table Text Block]
Schedule Of Contributions Defined Benefit Pension And Other Postretirement Plan [Table Text Block]
Cash Used In Investing Activities
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation
Performance Restricted Shares [Member]
Performance Restricted Shares [Member]
Performance Restricted Shares
Title of 12(b) Security
Schedule of Segment Reporting Information, by Segment [Table]
Fed Funds Effective Rate Overnight Index Swap Rate [Member]
Fitchburg
Fitchburg Gas and Electric Light Company
Fitchburg Gas And Electric Light Company [Member]
Fitchburg Gas and Electric Light Company. [Member]
Period 2
Period Two [Member]
Period two member.
Before August 1, 2022
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Derivatives
Period 4
Period Four [Member]
Period Four Member.
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value
Weighted Average Stock Price Forfeited
Subsegments [Domain]
Money Market Funds
Money Market Funds [Member]
Utility Plant
Public Utilities, Property, Plant and Equipment, Plant in Service
Debt repayment, Thereafter
Long-Term Debt, Maturity, after Year Five
Income Taxes
Income Tax Disclosure [Text Block]
First Mortgage Bonds Five Point Six Nine Percent Senior Secured Notes Due August Twenty One Twenty Fifty Four [Member]
First Mortgage Bonds 5.69% Senior Secured Notes Due August 21, 2054
First Mortgage Bonds Five Point Six Nine Percent Senior Secured Notes Due August One Twenty Twenty Fifty Four [Member]
Benefit Plan Costs
Benefit Plan Costs [Member]
Benefit Plan Costs [Member]
Massachusetts Customers [Member]
Massachusetts Customers [Member]
Document Information
Document Information [Table]
Other Noncurrent Liabilities
Other Liabilities, Noncurrent
Consolidated Entities [Axis]
Short-Term Debt
Interest Expense, Short-Term Borrowings
Interest Expense, Short-Term Borrowings, Total
Environmental Remediation Expense, before Recovery
Estimated Costs Accrued For Remediation
Legal Entity:
Legal Entity [Axis]
Changes in Working Capital Items:
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]
Letters of Credit Outstanding
Letters of Credit Outstanding, Amount
Plan assets measured at fair value
Plan Assets at Beginning of Year
Plan Assets at End of Year
Defined Benefit Plan, Plan Assets, Amount
Operating leases
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Income Tax Disclosure [Abstract]
Utility Plant:
Public Utilities, Property, Plant and Equipment [Abstract]
Bonds [Member]
Bonds [Member]
Unitil Energy Systems Inc
Unitil Energy Systems Inc
Unitil Energy Systems Inc [Member]
Unitil Energy Systems Inc
Restricted Stock Units Settled
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fully Vested Settled
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Fully Vested Settled.
Determine plan costs ultimate rate
Determine plan costs ultimate rate
Determine plan costs ultimate rate
Operating Lease Obligations (long-term portion)
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]
Statement of Income Location, Balance [Axis]
Capital Lease Obligations:
Capital Lease Obligations [Abstract]
Trading Symbol
Aggregate Market Value
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Aggregate Intrinsic Value
Share Based Compensation Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Grants in Period, Aggregate Intrinsic Value
Extinguishment of Debt [Axis]
Amount of capital expenditure approved by regulatory authority
Amount of capital expenditure approved by regulatory authority
Amount of capital expenditure approved by regulatory authority
Director [Member]
Directors
Public Utility Rate Change Percentage
Public Utility Rate Change Percentage
Public Utility Rate Change Percentage
7.98% Notes, Due June 1, 2031
Senior Notes Seven Point Nine Eight Percent Due June One Twenty Thirty One [Member]
Senior Notes Seven Point Nine Eight Percent Due June One Twenty Thirty One [Member]
Subsequent Event Type [Axis]
Financing Activities:
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Schedule of Impaired Financing Receivable [Table]
Total Payments
Lessee, Operating Lease, Liability, to be Paid
Lessee, Operating Lease, Liability, to be Paid, Total
Secured Overnight Financing Rate [Member]
Secured Overnight Financing Rate [Member]
Secured Overnight Financing Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Share Issued Weighted Average Fair Value
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Share Issued Weighted Average Fair Value
Weighted Average Stock Price Shares Issued
Debt Conversion [Table]
Equity Components [Axis]
Total Current Income Taxes
Current Federal, State and Local, Tax Expense (Benefit)
Less: Current Portion
Environmental Obligations
Accrued Environmental Loss Contingencies, Current
Equity Component [Domain]
Approved commitments for purchasing assets
Approved commitments for purchasing assets
Approved commitments for purchasing assets
Components Of Exchange Gas Receivable Abstract
Components of Exchange Gas Receivable [Abstract]
Document Annual Report
Power generation facility
Facility Power Capacity
Facility Power Capacity
Change in Discount Rate
Change In Discount Rate Assumption
Change in Discount Rate Assumption
DRP [Member]
DRP [Member]
DRP
Rate of Compensation Increase
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase
4.32% Senior Notes, Due November 1, 2047
Senior Notes Four Point Three Two Percent Due November One Twenty Forty Seven [Member]
Senior Notes Four Point Three Two Percent Due November One Twenty Forty Seven [Member]
Derivative, Fair Value, Net
Derivative, Fair Value, Net, Total
Fair value of derivative
Customer [Axis]
Subsidiaries [Member]
Subsidiaries [Member]
Avangrid Enterprises Inc [Member]
Avangrid Enterprises Inc [Member]
Avangrid Enterprises Inc
Public Utilities, Interim Rate Increase (Decrease), Amount
Public utilities interim increase decrease amount
Operation and Maintenance
Utilities Operating Expense, Maintenance and Operations
Utilities Operating Expense, Maintenance and Operations, Total
Construction Work in Progress
Public Utilities, Property, Plant and Equipment, Construction Work in Progress
Health Care Cost Trend Rate Assumed for Next Year
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year
Health care cost trend rate, assumed
Maximum
Maximum [Member]
Maximum
Fitchburg Performance Base Rate Adjustment Electric [Member]
Fitchburg Performance Base Rate Adjustment Electric [Member]
Fitchburg Performance Base Rate Adjustment Electric
Range [Axis]
Statistical Measurement [Axis]
Retirement Benefit Obligations
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits
Common Stock, Value, Issued
Beginning Balance
Ending Balance
Expenses associated with the program excluded from the revenue requirement as per order and adjusted increase amount will result in reasonable rates
Expenses associated with the program excluded from the revenue requirement as per order and adjusted increase amount will result in reasonable rates
Expenses associated with the program excluded from the revenue requirement as per order and adjusted increase amount will result in reasonable rates
Share Based Compensation Arrangement By Share Based Payment Liability Instrument Other Than Options Fully Vested Weighted Average Grant Date Fair Value
Share Based Compensation Arrangement By Share Based Payment Liability Instrument Other Than Options Fully Vested Weighted Average Grant Date Fair Value
Ending Liability Weighted Average Stock Price
3.70% Senior Notes, Due August 1, 2026
Senior Unsecured Notes Three Point Seven Zero Percent Due August One Twenty Twenty Six [Member]
Senior Unsecured Notes Three Point Seven Zero Percent Due August One Twenty Twenty Six [Member]
Components Of Gas Inventory Abstract
Components of Gas Inventory [Abstract]
Distributed Earnings
Distributed Earnings, Total
Less allocation of earnings and dividends to participating securities
December First Two Thousand And Twenty Four [Member]
December First Two Thousand And Twenty Four [Member]
December 1, 2024 [Member]
Consolidation, Policy [Policy Text Block]
Basis of Presentation
Income Taxes
Income Tax Related Liabilities
Income Tax Related Liabilities [Member]
Income tax related liabilities.
Secured Overnight Financing Rate (SOFR) [Member]
Type of Reserve [Domain]
Senior Notes Five Point Seven Four Percent Due August Twenty One Twenty Thirty Four [Member]
Senior Notes Five Point Seven Four Percent Due August Twenty One Twenty Thirty Four [Member]
5.74% Senior Notes, Due August 21, 2034
Other
Other 1 [Member]
Other 1.
Net Operating Loss Carryforwards
Deferred Tax Assets, Operating Loss Carryforwards
Deferred Tax Assets, Operating Loss Carryforwards, Total
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]
State Income Taxes, net
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent
State Income Taxes, net of Federal Income Tax Rate
Percentage of capitalization
Debt Instrument, Covenant Description
Allowance for Doubtful Accounts
Allowance For Doubtful Accounts Table Text Block [Table Text Block]
Allowance for Doubtful Accounts, Table.
Increase in cost
Increase Decrease Transfer Cost Amount
Increase Decrease Transfer Cost Amount
Entity Public Float
Entity Public Float
Increase (decrease) in annual revenue
Increase (Decrease) in Regulatory Clause Revenue
Taxes Other Than Income Taxes
Utilities Operating Expense, Taxes
Interest Payable, Current
Interest Payable
Inventory [Domain]
Costs and Expenses, Total
Costs and Expenses
Cost of Electric Sales
Common Stock Shares Issued Not Disclosed
Common Stock Shares Issued Not Disclosed
Common Stock Shares Issued Not Disclosed
Lease Obligations [Member]
Lease Obligations [Member]
Lease Obligations
Borrowing Limits Amounts Outstanding and Amounts Available under Credit Facility
Schedule of Debt [Table Text Block]
Less: Payments / Reductions
Accrual for Environmental Loss Contingencies, Payments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Registrant Name
Entity Registrant Name
Debt and Financing Arrangements
Debt Disclosure [Text Block]
Accumulated Benefit Obligation
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Accumulated Benefit Obligation
3.58% Mortgage Bonds, Due September 12, 2040
Mortgage Bonds Three Point Five Eight Percent Due September Fifteen Twenty Forty [Member]
Mortgage Bonds Three Point Five Eight Percent Due September Fifteen Twenty Forty Member.
Entity Voluntary Filers
Entity Voluntary Filers
5.74% Senior Notes, Due August 21, 2039
Senior Notes Five Point Seven Four Percent Due August Twenty One Twenty Thirty Nine [Member]
Senior Notes Five Point Seven Four Percent Due August Twenty One Twenty Thirty Nine [Member]
Total Reportable Segments
Total Reportable Segments [Member]
Total Reportable Segments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table]
Deferred Revenue Arrangement [Line Items]
Other Expense (Income), Net
Other Nonoperating Income (Expense)
Other Nonoperating Income (Expense), Total
State
Deferred State and Local Income Tax Expense (Benefit)
Share Based Payment Liability Instruments Other Than Options Fully Vested Dividend Equivalent Rights In Period Weighted Average Grant Date Fair Value
Share Based Payment Liability Instruments Other Than Options Fully Vested Dividend Equivalent Rights In Period Weighted Average Grant Date Fair Value
Dividend Equivalents Earned
Power generation capacity
Power Generation Capacity
Power generation capacity
Cybersecurity Risk Management Positions or Committees Responsible [Flag]
Deferred Regulatory and Other Charges
Change In Deferred Regulatory And Other Charges
The net change during the reporting period in deferred regulatory and other charges.
Consolidated Entities [Domain]
Common Stock Available For Future Sales
Common Stock Available for Future Sales
Future sales
Provision for Income Taxes
Total Income Tax Expense
Income Tax Expense (Benefit)
Income Tax Expense (Benefit)
Defined Benefit Plan, Target Plan Asset Allocations
Target Allocation
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage
Common stock dividend paid per share
Common Stock, Dividends, Per Share, Cash Paid
Rate Adjustment Mechanisms [Member]
Rate Adjustment Mechanisms
Rate Adjustment Mechanisms and Other
Defined Benefit Plan, Expected Future Benefit Payment, Year Five
2030
Proceeds from Issuance of Common Stock
Proceeds from Issuance of Common Stock
Proceeds from Issuance of Common Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Commitments And Contingencies [Line Items]
Commitments And Contingencies.
Entity Common Stock, Shares Outstanding
Liability Class [Axis]
Sublimit for the issuance of standby letters of credit
Sublimit For Issuance Of Standby Letters Of Credit
Sublimit for issuance of standby letters of credit
Consolidation Items [Axis]
Defined Benefit Plan, Expected Long-term Rate-of-Return on Assets Assumption
Defined Benefit Plan, Plan Assets, Expected Long-Term Rate-of-Return, Description
Federal Income Tax Expense (Benefit), Continuing Operations
Federal Income Tax Expense (Benefit), Continuing Operations, Total
Federal Income Taxes
Accounts Written Off
Accounts Receivable, Allowance for Credit Loss, Writeoff
Commitments and Contingencies
Commitments and Contingencies, Policy [Policy Text Block]
Property, Plant and Equipment Additions
Capital Expenditures
Payments to Acquire Property, Plant, and Equipment
Payments to Acquire Property, Plant, and Equipment, Total
Restricted Stock Units Granted
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period
Granted
TOTAL ASSETS
Segment Assets
Assets
Gas Inventory
Inventory, Policy [Policy Text Block]
Unitil Realty Corp Member
Unitil Realty Corp Member
Unitil Realty Corp Member
Income Statement [Abstract]
Senior Notes Five Point Nine Nine percent Due August Twenty One Twenty Forty Four [Member]
Senior Notes Five Point Nine Nine percent Due August Twenty One Twenty Forty Four [Member]
5.99% Senior Notes, Due August 21, 2044
3.78% Senior Notes, Due September 15, 2040
Senior Notes Three point Seventy Eight percent Due September Fifteen Twenty Forty [Member]
Senior Notes Three point Seventy percent Due September Fifteen Twenty Forty [Member]
Stock-based Employee Compensation
Share-Based Payment Arrangement [Policy Text Block]
Actuarial Loss Amortization
Defined Benefit Plan, Amortization of Gain (Loss)
Reclassification [Table]
Restriction on retained earnings for dividend payments
Regulatory Restrictions on Payment of Dividends
Other Deferred Charges
Other Deferred Charges [Member]
Other deferred charges.
Deferred Tax Provision
Deferred Income Tax Expense (Benefit)
Deferred Income Tax Expense (Benefit), Total
Average
Weighted Average [Member]
Sale of Stock, Number of Shares Issued in Transaction
Share sold under ATM program
Other
Other Customer [Member]
Common stock, shares issued
Stock Issued During Period, Shares, New Issues
Shares issued
Depreciation and Amortization
Depreciation, Depletion, and Amortization [Policy Text Block]
Schedule of Allocation of Plan Assets
Schedule of Allocation of Plan Assets [Table Text Block]
Earnings Per Share, Diluted, Total
Earnings Per Share, Diluted
Earnings per Common Share - Diluted
Common Stocks, Including Additional Paid in Capital
Common Equity (No par value, Authorized 25,000,000 Shares; Outstanding 16,192,345 and 16,192,345 Shares as of respective dates)
Significant Segment Financial Data
Schedule of Segment Reporting Information, by Segment [Table Text Block]
Weighted Average Number Of Share Outstanding Gross
Weighted Average Number Of Share Outstanding Gross
Weighted average common shares outstanding, gross
Operating Segments [Member]
Operating Segments
Long-Term Purchase Commitment [Table]
Dividends, Common Stock
Dividends, Common Stock, Total
Dividends
Percentage of fully-vested restricted stock units that directors will receive in cash when settled
Percentage Of Fully Vested Restricted Stock Units That Directors Will Receive In Cash When Settled
Percentage of fully-vested restricted stock units that Directors will receive in cash when settled.
City Area Code
Renewable Energy Portfolio Standards
Renewable Energy Portfolio Requirement [Member]
Renewable Energy Portfolio Requirement [Member]
First Mortgage Bonds 8.00% Senior Secured Notes, Due May 1, 2031
First Mortgage Bonds Eight Point Zero Zero Percent Senior Secured Notes Due May One Twenty Thirty One [Member]
First Mortgage Bonds Eight Point Zero Zero Percent Senior Secured Notes Due May One Twenty Thirty One [Member]
Auditor Name
Auditor Name
Increase in dividend declared amount per share
Common Stock Dividends Per Share Declared Increase Decrease
Common Stock, Dividends, Per Share, Declared, Increase (Decrease)
Finance Lease, Liability, Noncurrent
Other Noncurrent Liabilities (long-term portion)
Finance Lease Liability Noncurrent
Defined Benefit Obligations Member
Defined Benefit Obligations
Defined Benefit Obligations [Member]
Proceeds from lines of credit
Proceeds from Lines of Credit
Proceeds from Lines of Credit, Total
Electric and Gas Division [Member]
Electric and gas division.
Electric and Gas Division
Long-term debt, aggregate principal amount
Debt Instrument, Face Amount
Revolving credit facility, limit
Revolving credit facility
Line of Credit Facility, Maximum Borrowing Capacity
First Mortgage Bonds 8.49% Senior Secured Notes, Due October 14, 2024
First Mortgage Bonds Eight Point Four Nine Percent Senior Secured Notes Due October Fourteen Twenty Twenty Four [Member]
First Mortgage Bonds Eight Point Four Nine Percent Senior Secured Notes Due October Fourteen Twenty Twenty Four [Member]
Defined Benefit Plan [Table]
Tax Credit Carryforwards
Deferred Tax Assets, Tax Credit Carryforwards
Deferred Tax Assets, Tax Credit Carryforwards, Total
Granitestate Member
Granite State
GraniteState [Member]
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Number
Share Based Compensation Arrangement By Share Based Payment Liability Instruments Other Than Options Fully Vested Number
Beginning Restricted Stock Units Liability
Ending Restricted Stock Units Liability
Year that Ultimate Health Care Cost Trend Rate is reached
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate
Health care cost trend rate, ultimate rate in year
Operating lease, weighted average remaining lease term
Operating Lease, Weighted Average Remaining Lease Term
Plans' Assets, Projected Benefit Obligations (PBO), and Funded Status
Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block]
Stock Split Conversion Ratio
Stockholders' Equity Note, Stock Split, Conversion Ratio
Contractual Obligation, to be Paid, Year Five
2030
2029
Cash and Cash Equivalents
Cash and Cash Equivalents, Policy [Policy Text Block]
Energy Supply & Other Rate Adjustment Mechanisms
Contractual Obligations [Member]
Contractual Obligations [Member]
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]
Goodwill
Defined Benefit Plan, Expected Future Benefit Payment, Year Three
2028
Regulatory Liabilities
Regulatory Liabilities-noncurrent
Regulatory Liability, Noncurrent
Cash and Cash Equivalents at Beginning of Year
Cash and Cash Equivalents at End of Year
Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total
Fitchburg Gas System Enhancement Program
Fitchburg Gas System Enhancement Program [Member]
Fitchburg Gas System Enhancement Program [Member]
Operating Income
Operating Income (Loss)
Contractual Obligation, to be Paid, Year Three
2025
2028
Discount Rate
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate
Retained Earnings
Retained Earnings [Member]
Pre-65 retirees and Post -65 retirees
Pre and Post Sixty five retirees [Member]
Pre and Post Sixty five retirees [Member]
Income Taxes Table
Income Taxes [Table]
Assets, Noncurrent
Assets, Noncurrent, Total
Noncurrent assets
Asset Acquisition Consideration Transferred
Asset Acquisition, Consideration Transferred
Asset Acquisition, Consideration Transferred, Total
5.96% Senior Note Due to July 2, 2053
Senior Notes Five Point Nine Six Percent Due july Two Twenty Fift Three Member
Senior Notes Five Point Nine Six Percent Due july Two Twenty Fift Three Member
Total Noncurrent Liabilities
Liabilities, Noncurrent
Operating lease, weighted average discount rate percentage
Operating Lease, Weighted Average Discount Rate, Percent
Other Noncurrent Liabilities (long-term portion)
Operating Lease, Liability, Noncurrent
Operating Lease Obligations
Fair Value, Inputs, Level 1
Fair Value, Inputs, Level 1 [Member]
Fair Value Inputs Level 1
Class of Stock [Line Items]
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation
Cash Provided by Financing Activities
Less: Unamortized Debt Issuance Costs
Unamortized Debt Issuance Expense
Auditor Location
Auditor Location
Long-Term Debt [Member]
Long-Term Debt [Member]
Extinguishment of Debt, Type [Domain]
Total Other Noncurrent Assets
Noncurrent Assets Other Than Property Plant And Equipment
Non current assets other than property plant and equipment.
Public Utilities Approved Rate Increase Amount.
Approved annual increase in rates
Public Utilities Approved Rate Increase Amount
Contractual Obligation [Line Items]
Contractual Obligation [Line Items]
Contractual Obligation [Line Items]
Allowance for Doubtful Accounts
Allowance For Doubtful Accounts [Policy Text Block]
It represents Allowance For Doubtful Accounts
Fair Value of Marketable Securities
Marketable Securities [Table Text Block]
Total Balance at Beginning of Period
Total Balance at End of Period
Accrual for Environmental Loss Contingencies
Accrual for Environmental Loss Contingencies, Total
Environmental Exit Cost [Line Items]
Senior Unsecured Delayed Draw Term Loan Facility [Member]
Senior Unsecured Delayed Draw Term Loan Facility [Member]
Accrued Revenue
Trade and Other Accounts Receivable, Unbilled Receivables, Policy [Policy Text Block]
Guarantees outstanding
Guarantees Outstanding
Guarantees Outstanding
Weighted Average Non Vested Restricted Shares Excluded from Computation of Earnings Per Share
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]
Third Solicitation [Member]
Third Solicitation
Entity Interactive Data Current
Defined Benefit Plan, Plan Assets, Category [Axis]
Deferred Tax Liabilities
Deferred Tax Liabilities, Gross [Abstract]
Deferred Storm Charges
Electric Utilities [Member]
Electric Utilities [Member]
Statement of Income Location, Balance [Domain]
Time Restricted Shares
Time Restricted Shares [Member]
Time Restricted Shares [Member]
Operating Activities:
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Repayments of lines of credit
Repayments of Lines of Credit
Operating Revenues [Line Items]
Operating revenues.
Series 6
Series Six [Member]
Series 6 [Member]
Bangor
Bangor [Member]
Bangor [Member]
Issuance Date
Share Issued Date
Share issued date.
Percentage of total sales volumes revenue subject to RDM
Percentage Of Sales Volume
Percentage Of Sales Volume
Electric Vehicle Supply Equipment [Member]
Electric Vehicle Supply Equipment [Member]
Major Storm Cost Reserve Recovery [Member]
Major Storm Cost Reserve Recovery [Member]
Dividends per Common Share
Common Stock, Dividends, Per Share, Declared
Total Deferred Income Taxes
Deferred Federal, State and Local, Tax Expense (Benefit)
Add dilutive effect of:
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Entity Tax Identification Number
Revenues [Abstract]
Operating Revenues:
Schedule of Common Shares Activity
Schedule of Common Stock Outstanding Roll Forward [Table Text Block]
Regulatory Assets Harship Accounts Member
Regulatory Assets Harship Accounts
Regulatory Assets Harship Accounts [Member]
Regulated Operation, Regulatory Asset [Table]
Regulatory Assets Abstract
Regulatory Assets [Abstract]
Mid-Duration Storage
Mid-Duration Storage
Mid-Duration Storage
Performance Restricted [Member]
Performance Restricted [Member]
Performance Restricted
Total Operating Expenses
Utilities Operating Expense
Maine Natural Inc
Maine Natural Inc [Member]
Maine Natural Inc [Member]
At The Market Offering [Member]
At The Market Offering [Member]
ATM
Local Phone Number
Post sixty five retirees member.
Post Sixty Five Retirees [Member]
Post-65 retirees
NPBC Recognized
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Other Current Liabilities
Other Liabilities, Current
Unrecognized share based compensation
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount
Regulatory Liability [Line Items]
Auditor Opinion [Text Block]
Auditor Opinion
Qualified Clean Energy Member
Qualified Clean Energy
Qualified Clean Energy [Member]
Finance Lease, Liability, to be Paid, Year Two
2027
Summary of Company's Contractual Obligations for Log-term Debt
Contractual Obligation Fiscal Year Maturity Long Term Debt Schedule [Table Text Block]
Contractual obligation fiscal year maturity long term debt schedule.
2.64% Senior Secured Notes, Due December 18, 2030
Two Point Six Four Percent Due December Eighteen Twenty Thirty [Member]
Two Point Six Four Percent Due December Eighteen Twenty Thirty Member
Cancellations under the stock plan
Share Based Compensation Arrangement By Share Based Payment Award Options Cancelled In Period
Share Based Compensation Arrangement by Share Based Payment Award, Options, Cancelled in Period
Schedule of The Time Restricted Shares and Performance Restricted Share [Table Text Block]
Schedule of The Time Restricted Shares and Performance Restricted Share [Table Text Block]
Schedule of Time Restricted Shares and Performance Restricted Share
Accounting Policies [Abstract]
Senior Notes Five Point Six Nine Percent Due Twenty Fifty Four [Member]
Senior Notes Five Point Six Nine Percent Due Twenty Fifty Four [Member]
5.69% Senior Note Due to 2054
Regulatory Liabilities
Increase (Decrease) in Regulatory Liabilities
M E Member
Maine
ME [Member]
Total Operating Revenues
Revenue from Contract with Customer, Excluding Assessed Tax
Components of Gas Inventory
Schedule of Utility Inventory [Table Text Block]
Pro Forma Weighted Average Shares Outstanding, Diluted
Restricted stock and restricted stock units
Natural gas available under firm contract per day of year-round and seasonal transportation and underground storage capacity to distribution facilities
Oil and Gas, Delivery Commitment, Daily Production
Requested annual increase in rates
Public Utilities, Requested Rate Increase (Decrease), Amount
Senior Notes Five Point Seven Four Percent Due Twenty Thirty Four [Member]
Senior Notes Five Point Seven Four Percent Due Twenty Thirty Four [Member]
5.74% Senior Note Due to 2034
Lessee, Operating Lease, Liability, to be Paid, Year Four
2029
Cash and Cash Equivalents
Cash and Cash Equivalents [Member]
Beginning Restricted Stock Units
Ending Restricted Stock Units
Sharebased Compensation Arrangement By Sharebased Payment Award Equity Instruments Other Than Options Fully Vested Number
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Fully Vested, Number
Class of Stock [Domain]
Restricted stock that may be awarded in any one calendar year to any one participant
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant
Share compensation recognition period
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition
Stock, Class of Stock [Table]
Contractual Obligation, to be Paid, Year One
2023
2026
Contractual Obligation Fiscal Year Maturity Schedule Table
Contractual Obligation Fiscal Year Maturity Schedule [Table]
Entity Emerging Growth Company