75000 - Document - Cover Page
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75010 - Statement - CONSOLIDATED STATEMENTS OF EARNINGS (UNAUDITED)
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75020 - Statement - CONSOLIDATED BALANCE SHEETS (UNAUDITED)
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75030 - Statement - CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical)
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75040 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)
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75050 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (UNAUDITED)
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75060 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK EQUITY (UNAUDITED) (Parenthetical)
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995455 - Disclosure - Summary of Significant Accounting Policies
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995465 - Disclosure - Dividends Declared Per Share
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995475 - Disclosure - Segment Information
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995485 - Disclosure - Debt and Financing Arrangements
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995495 - Disclosure - Equity
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995505 - Disclosure - Derivatives
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995515 - Disclosure - Regulatory Matters
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995525 - Disclosure - Environmental Matters
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995535 - Disclosure - Income Taxes
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995545 - Disclosure - Retirement Benefit Obligations
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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 - Dividends Declared Per Share (Tables)
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995585 - Disclosure - Segment Information (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 - Environmental Matters (Tables)
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995625 - Disclosure - Income Taxes (Tables)
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995635 - Disclosure - Retirement Benefit Obligations (Tables)
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995645 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail)
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995655 - Disclosure - Summary of Significant Accounting Policies - Components of Gas and Electric Operating Revenue (Detail)
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995665 - Disclosure - Estimated Percentage of Decoupled Sales (Details)
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995675 - Disclosure - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts Included in Accounts Receivable Net (Detail)
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995685 - Disclosure - Summary of Significant Accounting Policies - Components of Accrued Revenue (Detail)
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995695 - Disclosure - Summary of Significant Accounting Policies - Components of Exchange Gas Receivable (Detail)
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995705 - Disclosure - Components of Gas Inventory (Detail)
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995715 - Disclosure - Summary of Significant Accounting Policies - Regulatory Assets (Detail)
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995725 - Disclosure - Regulatory Liabilities (Detail)
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995735 - Disclosure - Summary of Significant Accounting Policies - Fair Value of Marketable Securities (Detail)
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995745 - Disclosure - Components of Energy Supply Obligations (Detail)
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995755 - Disclosure - Dividends Declared Per Share (Detail)
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995765 - Disclosure - Segment Information - Significant Segment Financial Data (Detail)
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995775 - Disclosure - Segment Information (Additional Information) (Details)
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995785 - Disclosure - Debt and Financing Arrangements - Details On Long Term Debt (Detail)
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995795 - Disclosure - Debt and Financing Arrangements - Details On Long Term Debt (Parenthetical) (Detail)
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995805 - Disclosure - Debt and Financing Arrangements - Estimated Fair Value Of Long Term Debt (Detail)
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995815 - Disclosure - Debt and Financing Arrangements - Additional Information (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 - Classification Of The Company Lease Obligations (Detail)
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995845 - Disclosure - Debt and Financing Arrangements - Future Operating Lease Payment Obligations And Future Minimum Lease Payments Under Capital Leases (Detail)
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995855 - Disclosure - Equity - Additional Information (Detail)
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995865 - Disclosure - Equity - Schedule of Common Shares Activity (Details)
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995875 - Disclosure - Equity - Time Restricted Shares and Performance Restricted Shares activity (Details)
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995885 - Disclosure - Equity - Restricted Stock Units Issued (Detail)
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995895 - Disclosure - Equity - Reconciles Basic and Diluted Earnings Per Share (Details)
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995905 - Disclosure - Derivatives (Additional Information) (Details)
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995915 - Disclosure - Regulatory Matters - Additional Information (Detail)
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995925 - Disclosure - Regulatory Matters - Additional Information (Detail 1)
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995935 - Disclosure - Environmental Matters - Additional Information (Detail)
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995945 - Disclosure - Environmental Matters - Company's Liability for Environmental Obligations (Detail)
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995955 - Disclosure - Income Taxes - Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate (Detail)
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995965 - Disclosure - Income Taxes - Additional Information (Detail)
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995975 - Disclosure - Retirement Benefit Obligations - Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations (Detail)
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995985 - Disclosure - Retirement Benefit Obligations - Additional Information (Detail)
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995995 - Disclosure - Retirement Benefit Obligations - Components of Retirement Plan Costs (Detail)
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Line of Credit Facility [Line Items]
Line of Credit Facility [Line Items]
Scenario [Axis]
Federal tax credit carryforward
Federal Tax Credit Carryforward
Federal Tax Credit Carryforward
Abenaki [Member]
Abenaki [Member]
Abenaki [Member]
Business Combination, Recognized Liability Assumed, Liability, Noncurrent
Business Combination, Recognized Liability Assumed, Liability, Noncurrent, Total
Acquisition noncurrent liabilities
Increase (Decrease) in Contract with Customer, Asset
Accrued Revenue
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]
3.52% Senior Notes, Due November 1, 2027
July 1, 2024
July First Two Thousand And Twenty Four Member
July First Two Thousand And Twenty Four [Member]
Accounts Payable
Accounts Payable, Total
Accounts Payable
Debt Disclosure [Text Block]
Debt and Financing Arrangements
Regulatory Assets, Noncurrent
Regulatory Assets – noncurrent
Regulatory Assets
Purchases of natural gas, contract duration
Contract Duration
Contract duration.
Program duration
Operating Lease, Liability, Total
Operating Lease, Liability
Amount of Lease Obligations Recorded on Consolidated Balance Sheets
Total Operating Lease Obligations
Interest Expense, Operating and Nonoperating
Interest Expense, Operating and Nonoperating, Total
Interest Expense
Revenue Increase Approved By Regulator
Revenue Increase Approved By Regulator
Revenue increase approved by regulator
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]
Fair Value of Long Term Debt
Defined Benefit Plan, Benefit Obligation, Benefits Paid
Benefit payments under SERP Plan
Benefits Paid
Benefits Paid
Agreement [Domain]
Agreement [Domain]
Public Utilities, Requested Return on Equity, Percentage
Return on equity
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested In Period Weighted Average Grant Date Fair Value
Share based Compensation Arrangement by Share based Payment Award, Equity Instruments Other than Options, Nonvested in Period, Weighted Average Grant Date Fair Value.
Restricted Stock Units Granted
Regulatory liability recovery refund.
Regulatory Liability Recovery Refund
Regulatory liability, expected flow back to customers
Debt Instrument, Basis Spread on Variable Rate
Credit facility, daily fluctuating rate of interest
Fixed Income Funds [Member]
Fixed Income Funds
Commitments and Contingencies
Commitments and Contingencies (Notes 7 & 8)
Senior Notes Five Point Eight Seven Percent Due Twenty Forty One [Member]
Senior Notes Five Point Eight Seven Percent Due Twenty Forty One [Member]
5.87 % Senior Note Due to 2041
Weighted Average Number of Shares Outstanding, Diluted, Total
Weighted Average Number of Shares Outstanding, Diluted
Adjusted weighted average number of shares outstanding used in the calculation of diluted earnings per common share
Weighted Average Common Shares Outstanding - Diluted
Other Receivables, Net, Current, Total
Other Receivables, Net, Current
Total Exchange Gas Receivable
Exchange Gas Receivable
RSU Settlement Member
RSU Settlement
RSU Settlement [Member]
Lessee, Operating Lease, Term of Contract
Lease term
Cost Of Issue
Cost Of Issue
Cost of issue
Minimum [Member]
Minimum [Member]
Assets, Noncurrent [Abstract]
Other Noncurrent Assets:
The net change during the reporting period in exchange gas financing.
Increase Decrease In Gas Inventory Financing
Net (Decrease) Increase in Exchange Gas Financing
Program [Axis]
Program [Axis]
Fitchburg Grid Modernization [Member]
Fitchburg Grid Modernization [Member]
Fitchburg - Grid Modernization
First Mortgage Bonds Four Point Eighteen Percent Senior Secured Notes Due November Thirty Twenty Forty Eight [Member]
First Mortgage Bonds Four Point Eighteen Percent Senior Secured Notes Due November Thirty Twenty Forty Eight [Member]
4.18% Senior Secured Notes Due November 30, 2048
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
Ending Restricted Stock Units
Beginning Restricted Stock Units
Debt Instrument, Interest Rate, Effective Percentage
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Other Subsidiaries [Member]
Other Subsidiaries [Member]
Unitil Service; Unitil Realty; and Unitil Resources
Other Subsidiaries
Order [Domain]
Order [Domain]
Preferred Stock, Shares Outstanding, Ending Balance
Preferred Stock, Shares Outstanding, Beginning Balance
Preferred Stock, Shares Outstanding
Preferred stock, outstanding
Inventory [Axis]
Finance Lease, Liability, to be Paid, Year Two
2027
2028
Capitalization, Long-term Debt and Equity
Total Capitalization
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage
Restricted stock vesting percentage annually
Accrued Environmental Loss Contingencies, Noncurrent
Environmental Obligations
Noncurrent Balance at End of Period
Segment Reporting [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Remainder of Fiscal Year
Expected additional benefit payments for the remainder of 2020
Regulatory Assets, Current
Less: Current Portion of Regulatory Assets
Regulatory Assets – Current
Debt Instrument, Face Amount
Long-term debt, aggregate principal amount
Income Tax Expense (Benefit), Total
Income Tax Expense (Benefit)
Income Tax Expense (Benefit)
Provision for Income Taxes
Electric
Electric [Member]
Electric [Member]
Electric
ATM [Member]
ATM Member
ATM
Deferred Compensation Plan [Member]
Deferred Compensation Plan [Member]
Deferred Compensation Plan [Member]
Deferred Compensation Plan
Supply Commitment [Table Text Block]
Components of Energy Supply Obligations
Share Based Compensation Arrangement by Share Based Payment Award, Nonvested Shares, Outstanding, Number.
Share Based Compensation Arrangement By Share Based Payment Award Nonvested Options Outstanding Number
Restricted stock non-vested
Schedule of Costs of Retirement Plans [Table Text Block]
Components of Retirement Plan Costs
Debt Conversion [Table]
Restricted Stock Units (RSUs) [Member]
Restricted Stock Units (RSUs)
It represents Supply Commitment.
Supply Commitment [Policy Text Block]
Energy Supply Obligations
Gas
Gas [Member]
Gas [Member]
Gas
Accrued Revenue
Unbilled Contracts Receivable
Total Accrued Revenue
GSEP 2027
GSEP Two Thousand Twenty Seven [Member]
GSEP Two Thousand Twenty Seven [Member]
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
Energy [Domain]
Debt instrument variable interest rate additional spread.
Debt Instrument Variable Interest Rate Additional Spread
Debt instrument variable interest rate additional spread
Repayments of Lines of Credit
Repayments of lines of credit
Operating Segments [Member]
Operating Segments
Environmental Exit Cost [Line Items]
Extended long-term renewable contracts
Extended Renwel Periods
Extended Renwel Periods
Revolving Credit Facility, Limit
Line of Credit Facility, Maximum Borrowing Capacity
Revolving credit facility
Accrued Environmental Loss Contingencies, Current
Environmental Obligations
Less: Current Portion
Components of gas operating revenue and electric operating revenue.
Components Of Gas Operating Revenue And Electric Operating Revenue [Table Text Block]
Components of Gas and Electric Operating Revenue
Gross proceeds
Common Stock Gross Proceeds
Common Stock Gross Proceeds
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate
Discount Rate
Health care cost trend rate, ultimate rate in year
Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate
Year that Ultimate Health Care Cost Trend Rate is reached
Subsequent Event Type [Domain]
Subsequent Event Type [Domain]
Inventory [Domain]
Less: Payments / Reductions
Accrual for Environmental Loss Contingencies, Payments
Less: Payments / Reductions
Environmental Matters
Environmental Loss Contingency Disclosure [Text Block]
Environmental Remediation Expense, before Recovery
Estimated Costs Accrued For Remediation
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount
State Income Taxes, net of Federal Income Tax
Amounts of pension and other post retirement benefit costs capitalized and deferred.
Defined Benefit Plan Capitalized And Deferred
Amounts Capitalized and Deferred
Schedule of Long-Term Debt Instruments [Table]
Distributed Earnings
Distributed Earnings, Total
Less allocation of earnings and dividends to participating securities
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
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]
5.90% Notes, Due December 15, 2030
Environmental and Rate Case Costs and Other Expenditures [Member]
Environmental And Rate Case Costs And Other Expenditures [Member]
Environmental and Rate Case Costs and Other Expenditures
Common Shares [Table]
Common Shares [Table]
Statement of Financial Position Balance [Axis]
Statement of Financial Position Balance [Axis]
Income Statement [Abstract]
Common Stocks, Including Additional Paid in Capital
Common Equity (No par value, Authorized 25,000,000 shares; Outstanding 18,225,964, 16,291,395 and 17,919,191 Shares)
With Effect From First January Two Thousand And Twenty Three [Member]
With Effect From First January Two Thousand And Twenty Three [Member]
Income Tax, Examination [Table]
Defined benefit plan, assumed health care cost trend rate, description
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period
Forfeited
Forfeited
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]
Goodwill
Subsequent Events, Policy [Policy Text Block]
Subsequent Events
Vesting [Axis]
Utilities Operating Expense, Depreciation and Amortization
Depreciation and Amortization
Depreciation & Amortization Expense
Earnings Per Share, Basic, Total
Earnings Per Share, Basic
Basic
Earnings Per Common Share - Basic
Document Period End Date
Period End Date
Inventory, Raw Materials and Supplies, Gross, Total
Inventory, Raw Materials and Supplies, Gross
Materials and Supplies
Document Information [Table]
Document Information
Environmental Exit Cost [Table]
Allowance for Doubtful Accounts Included in Accounts Receivable Net Detail [Abstract]
Allowance For Doubtful Accounts Included In Accounts Receivable Netdetail Abstract
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation
Less: Accumulated Depreciation
Tax Period [Axis]
Payments to Acquire Property, Plant, and Equipment, Total
Payments to Acquire Property, Plant, and Equipment
Capital Expenditures
Property, Plant and Equipment Additions
Debt Instrument [Line Items]
Debt Instrument [Line Items]
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
Restricted Stock Units Settled
Common Stock, Shares Authorized
Common Stock Authorized
Common stock, shares authorized
Effective Income Tax Continuing Operations Amount
Effective Income Tax Continuing Operations Amount
Effective Income Tax Continuing Operations Amount
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
Restricted Stock Units Granted
Operating Lease Liabilities, Payments Due [Abstract]
Operating Lease Obligations:
Health care cost trend rate, ultimate rate
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate
Ultimate Health Care Cost Trend Rate
Period Type [Axis]
Period Type Axis
Prepaid Expense and Other Assets, Current
Prepayments and Other
Estimated Percentage of Decoupled Sales
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]
Trade and Other Accounts Receivable, Unbilled Receivables, Policy [Policy Text Block]
Accrued Revenue
Group Four [Member]
Group Four [Member]
Group Four
Site Contingency [Table]
Goodwill, Period Increase (Decrease)
Goodwill, Period Increase (Decrease), Total
Increase in goodwill
Dividends [Domain]
Line items represent receivables.
Receivables [Line Items]
Lease obligation.
Lease Obligation
Total Lease Obligations
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]
6.96% Senior Secured Notes, Due September 1, 2028
Settlement Agreement [Member]
Settlement Agreement [Member]
Debt Instrument, Redemption, Period Five [Member]
Recovered over the next seven years
Schedule Of Future Minimum Payments For Obligations [Table Text Block]
Schedule Of Future Minimum Payments For Obligations [Table Text Block]
Future Operating Lease Payment Obligations and Future Minimum Lease Payments under Capital Leases
Postemployment Retirement Benefits [Member]
Retirement Benefits
Overall Cost Of Capital Percentage
Overall Cost Of Capital Percentage
Overall cost of capital percentage
Debt Instrument, Interest Rate, Stated Percentage
Stated interest rate
Long-term debt, stated interest rate
Costs and Expenses, Total
Costs and Expenses
Cost of Sales
Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]
Unamortized Debt Issuance Expense
Less: Unamortized Debt Issuance Costs
Segment Assets
Assets
TOTAL ASSETS
Segment Assets
Title of 12(b) Security
Period Type [Domain]
Period Type Domain
Maine Natural Gas Corporation [Member]
Maine Natural Gas Corporation [Member]
Maine Natural Gas Corporation
Deferred Revenue Arrangement [Line Items]
Regulatory Asset, Total
Regulatory Assets
Regulatory assets
Regulatory Assets
Loss Contingency, Nature [Domain]
Goodwill
Goodwill
Goodwill, Ending Balance
Goodwill, Beginning Balance
Goodwill, Total
Preferred Stock, Value, Issued
Preferred Stock
Other Restructuring [Member]
Other Restructuring
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 March 31, 2026
Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent, Total
Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent
Retirement Benefit Obligations
Senior Notes Five Point Six Two Percent Due Twenty Thirty Six [Member]
Senior Notes Five Point Six Two Percent Due Twenty Thirty Six [Member]
5.62 % Senior Note Due to 2036
Finance Lease, Liability, to be Paid, Year Three
2028
2029
Regulatory Asset [Domain]
Operating Lease, Payments
Operating lease obligations
Senior Notes Five Point Six Two Percent Due April Thirty Two Thousand Thirty Six [Member]
Senior Notes Five Point Six Two Percent Due April Thirty Two Thousand Thirty Six [Member]
5.62% Senior Notes, Due April 30, 2036
Gas System Enhancement Recovery Cap Rate
Gas System Enhancement Recovery Cap Rate
Recovery cap rate
Stock Split Conversion Ratio
Stockholders' Equity Note, Stock Split, Conversion Ratio
Effective Income Tax Rate Reconciliation, Percent, Total
Effective Income Tax Rate Reconciliation, Percent
Effective Income Tax Rate
Length of Pipeline
Length of natural gas transmission pipeline.
Length Of Pipeline
Variable Rate [Axis]
Lessee, Operating Lease, Liability, to be Paid, Remainder of Fiscal Year
Rest of 2026
Interest Paid, Excluding Capitalized Interest, Operating Activity
Interest Paid
Proceeds from Issuance of Long-Term Debt
Proceeds from Issuance of Long-Term Debt, Total
Issuance of Long-Term Debt
FERC Transmission Formula Rate Proceedings [Member]
FERC Transmission Formula Rate Proceedings [Member]
Propane [Member]
Propane
Lessee, Operating Lease, Liability, to be Paid, Year One
2027
Capitalization, Long-term Debt and Equity [Abstract]
Capitalization:
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
Utilities Operating Expense
Total Operating Expenses
Revenue Cap
Revenue Cap
Revenue cap
Northern Utilities-Base Rates-New Hampshire
Northern Utilities - Base Rates - New Hampshire [Member]
Northern Utilities - Base Rates - New Hampshire [Member]
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited
Performance restricted shares, shares forfeited
Segment Reporting [Table Text Block]
Significant Segment Financial Data
Interest and Other Income
Interest Income
Interest and Other Income
Interest Income
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
AWC-NH [Member]
AWC-NH [Member]
AWC-NH [Member]
Pre-65 retirees
Pre Sixty Five Retirees [Member]
Pre sixty five retirees member.
Equity, Attributable to Parent
Total Stockholders' Equity
Beginning Balance
Ending Balance
Other Changes in Working Capital Items
Increase (Decrease) in Other Current Assets and Liabilities, Net
Other Changes in Working Capital Items
Construction Advances
Construction Advances
Construction Advances
Construction Advances
Net Proceed Common Stock
Net Proceed Common Stock
Net Proceed
Other Assets, Noncurrent
Other Assets
Arrangements and Non-arrangement Transactions [Domain]
Income Tax Disclosure [Text Block]
Income Taxes
Non-Participating Securities [Member]
Non-Participating Securities Member
Non-Participating Securities [Member]
Fair Value of Restricted Stock Units to be settled in cash.
Fair Value Of Restricted Stock Units Settled In Cash
Fair value of liabilities associated with fully vested RSUs that will be settled in cash
Long-term Debt, Fair Value
Estimated Fair Value of Long-Term Debt
Weighted Average [Member]
Average
Number of reportable segments
Number of Reportable Segments
Residential
Residential
Residential [Member]
Oil and Gas [Policy Text Block]
Acquisition of Bangor Natural Gas Company
Weighted-Average Stock Price
Weighted Average Stock Price
Basis of Accounting, Policy [Policy Text Block]
Basis of Presentation
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
Restricted Stock Units Settled
Effective Income Tax Rate Reconciliation, Tax Credit, Percent
Effective Income Tax Rate Reconciliation, Tax Credit, Percent, Total
Production Tax Credit Percent
Production Tax Credit Percent
Long-term Debt
Long-Term Debt
Credit Facility [Axis]
Schedule of Utility Inventory [Table Text Block]
Components of Gas Inventory
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]
3.72% Senior Notes, Due November 1, 2027
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
Lessee, Operating Lease, Liability, to be Paid, after Year Five
2031-2035
2031-2035
Interest Income (Expense), Nonoperating
Interest Expense, Net
Total Interest Expense, Net
Credit Facility [Member]
Credit Facility
Credit Facility Member
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]
6.32% Senior Secured Notes, Due September 15, 2036
Repayments of Long-Term Debt, Total
Repayments of Long-term Debt
Repayment of Long-Term Debt
Long term debt repayments
Inventory, Policy [Policy Text Block]
Gas Inventory
Restricted Stock [Member]
Restricted Stock
Spending cap
Contractual Obligation, Total
Contractual Obligation
Spending cap
Schedule of Common Shares Activity
Schedule of Nonvested Share Activity [Table Text Block]
Revolving Credit Facility [Member]
Revolving Credit Facility
Senior notes two point six four percent due december eighteen twenty thirty.
Senior Notes Two Point Six Four Percent Due December Eighteen Twenty Thirty [Member]
2.64% Senior Secured Notes, Due December 18, 2030
Loss Contingency Nature [Axis]
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 [Member]
Dividend And Distribution Reinvestment And Share Purchase Plan [Member]
Dividend and Distribution Reinvestment and Share Purchase Plan
Net Utility Plant Acquired
Net Utility Plant Acquired
Acquired working capital
Geographical [Domain]
Geographical [Domain]
Range [Axis]
Range [Axis]
Money Market Funds [Member]
Money Market Funds
Public Utilities, Property, Plant and Equipment, Common
Common
Entity Interactive Data Current
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]
7.72% Senior Notes, Due December 3, 2038
Equity [Table]
Equity [Table]
Lessee, Operating Lease, Liability, to be Paid, Year Three
2028
2029
NEW HAMPSHIRE
New Hampshire
Asset Acquisition, Consideration Transferred
Asset Acquisition, Consideration Transferred, Total
Asset Acquisition Consideration Transferred
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Schedule of Earnings Per Share, Basic and Diluted
Taxes Payable
Taxes Payable, Current, Total
Taxes Payable, Current
Property, Plant, and Equipment [Policy Text Block]
Utility Plant
Fitchburg Gas Company [Member]
Fitchburg Gas Company
Fitchburg gas company
Decrease in Capital Lease Obligations
Increase (decrease) in capital lease obligations.
Increase Decrease In Capital Lease Obligations
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
Dividend Equivalents Earned
Gas Segment [Member]
Gas Segment [Member]
Gas Segment
Carrying costs
Additional Carrying Costs
Additional Carrying Costs
Business Combination, Date of Acquisition Agreement
Acquisition Date
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
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
5.70% Notes, Due July 2, 2033
O2025 M7 Dividends [Member]
O2025 M7 Dividends [Member]
Regulatory Liabilities [Abstract]
Regulatory Liabilities Abstract
Product and Service [Axis]
Description of the components and amounts included in Exchange Gas Receivable.
Schedule Of Other Accounts Receivable [Table Text Block]
Components of Exchange Gas Receivable
Retained Earnings (Accumulated Deficit), Total
Retained Earnings (Accumulated Deficit)
Retained Earnings
Retained Earnings
Public Utilities Disclosure [Text Block]
Regulatory Matters
Other Customer [Member]
Other
Group One
Group One [Member]
Group One [Member]
Text Block [Abstract]
Taxes Other Than Income Taxes
Utilities Operating Expense, Taxes
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.
Increase (Decrease) in Accounts Payable, Total
Increase (Decrease) in Accounts Payable
Accounts Payable
Working Capital
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]
Dividend Amount
Common Stock, Dividends, Per Share, Declared
Dividends per Common Share
Exchange Gas Obligation [Policy Text Block]
Exchange Gas Obligation [Policy Text Block]
Exchange Gas Obligation
Revenues [Abstract]
Operating Revenues
Share Price
Share price
Vesting [Domain]
Liabilities, Noncurrent [Abstract]
Noncurrent Liabilities:
Business Combination, Goodwill, Expected Tax Deductible, Amount
Deductible portion of goodwill
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase
Rate of Compensation Increase
New England [Member]
New England [Member]
ISO-NE Obligations
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract]
Changes in Working Capital Items:
Arrearage Management Program [Member]
Arrearage Management Program [Member]
Arrearage Management Program
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Restricted stock vesting period
Shares Issued, Price Per Share
Common stock price per share
Regulatory Assets Deferred Costs
Regulatory Assets Deferred Costs
Regulatory assets deferred cost
Public Utilities, Interim Rate Increase (Decrease), Amount
Public utilities interim increase decrease amount
Restricted Stocks [Table]
Restricted Stocks [Table]
Stock Issued During Period, Shares, New Issues
Common stock, shares issued
Shares Issued
Other Noncurrent Asset [Member]
Other Noncurrent Asset [Member]
Information by type of investments.
Investment Types [Axis]
Summary of Investments, Other than Investments in Related Parties, by Type
Gas Division [Member]
Gas Division [Member]
Gas Division [Member]
Public Utilities, Approved Equity Capital Structure, Percentage
Percentage of approved return on equity, reflecting on equity
Percentage of approved return on equity, reflecting on equity
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided
Regulatory assets approved increase in revenue due to be recovered
Regulatory assets approved increase in revenue due to be recovered
Variable Rate [Domain]
Share-based Compensation Arrangement by Share-based Payment Awards Equity Instrument Other than Options Outstanding Weighted Average Exercise Price
Sharebased Compensation Arrangement By Sharebased Payment Awards Equity Instrument Other Than Options Outstanding Weighted Average Exercise Price
Weighted-Average Stock Price
Noncurrent assets
Assets, Noncurrent
Assets, Noncurrent, Total
Estimate program cost
Estimated Program Cost
Estimated Program Cost
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total
Property, Plant, and Equipment, Accumulated Depreciation, Depletion, and Amortization
Net Utility Plant, accumulated amortization
Business Combination, Price of Acquisition, Expected
Business Combination Price Of Acquisition Expected
Operating Lease, Cost
Total rental expense under operating leases
Property, Plant and Equipment, Type [Axis]
Income Tax, Policy [Policy Text Block]
Income Taxes
Components of Accrued Revenue [Abstract]
Components Of Accrued Revenue Abstract
Granite state member.
Granite State [Member]
Granite State
Massachusetts And Maine [Member]
Massachusetts and maine.
Massachusetts And Maine [Member]
Service Cost
Service Cost
Defined Benefit Plan, Service Cost
Fair Value Hierarchy and NAV [Axis]
GSEP Two Thousand Twenty Five [Member]
GSEP Two Thousand Twenty Five [Member]
GSEP 2025
Defined Benefit Plan [Table]
Unitil corporation.
Unitil Corporation [Member]
Unitil Corporation
Electric Division [Member]
Electric Division [Member]
Electric Division [Member]
Track One [Member]
Track One [Member]
Public Utilities, Property, Plant and Equipment, Construction Work in Progress
Construction Work in Progress
Available Revolving Credit Facility
Line of Credit Facility, Remaining Borrowing Capacity
Senior notes three point seven eight percent due september fifteen twenty fourty.
Senior Notes Three Point Seven Eight Percent Due September Fifteen Twenty Fourty [Member]
3.78% Senior Notes, Due September 15, 2040
Base Rate [Member]
Operating Lease, Liability, Current
Operating Lease Obligations
Operating Lease Obligations (current portion)
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
Dividend Equivalents Earned
GSEP Two Thousand Twenty Six [Member]
GSEP Two Thousand Twenty Six [Member]
GSEP 2026
Waters [Member]
Waters [Member]
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 March 31, 2026
Weighted Average Stock Price as of December 31, 2025
Income Tax Examination [Line Items]
Customer [Domain]
Derivative Assets [Member]
Derivative Assets [Member]
Derivative Assets
Imputed Interest On Capital Leases
Imputed Interest On Capital Leases
Less: Interest
Less: Interest
Regulatory Liability, Total
Regulatory Liabilities
Regulatory Liabilities
Regulatory Liability
Effective Income Tax Rate Reconciliation, Tax Credit, Amount
Effective Income Tax Rate Reconciliation, Tax Credit, Amount, Total
Production Tax Credit
Production Tax Credit
Business Acquisition Liabilities Assumed
Business Combination, Recognized Liability Assumed, Liability
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities, Total
Liabilities and Equity
TOTAL LIABILITIES AND CAPITALIZATION
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]
7.37% Notes, Due January 15, 2029
Lessee, Operating Lease, Liability, to be Paid, Year Two
2027
2028
Debt Instrument, Description of Variable Rate Basis
Description of variable rate basis
Goodwill, Measurement Period Adjustment
Adjustment to goodwill
Document Fiscal Period Focus
Remediation costs
Remediation costs
Remediation costs
Derivatives, Fair Value [Line Items]
Short-Term Debt, Total
Short-term Debt
Short-Term Borrowings Outstanding
Short-Term Debt
Purchase commitments for data sharing platform investments
Purchase commitments for data sharing platform investments
Purchase commitments for data sharing platform investments
Performance Shares [Member]
Performance Restricted Shares
Environmental Remediation Expense, before Recovery, Statement of Income or Comprehensive Income [Extensible Enumeration]
Schedule of Capital Leases Obligations [Table Text Block]
Schedule Of Capital Leases Obligations [Table Text Block]
Classification of the Company Lease Obligations
Regulatory Amortization of Excess ADIT Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Percent
Storm Cost Deferral Petition [Member]
Storm Cost Deferral Petition [Member]
Storm Cost Deferral Petition
Acquisition, Net of Cash Acquired
Payments to Acquire Businesses, Net of Cash Acquired
Payments to Acquire Businesses, Net of Cash Acquired, Total
Acquisition of Businesses, Net of Cash Acquired
Letters of Credit Outstanding, Amount
Total Outstanding Amount
Sale of Stock [Axis]
Intangible Asset, Finite-Lived, Useful Life
Amortization period
Public Utilities, Approved Return on Equity, Percentage
Percentage of approved return on equity
Percentage of approved return on equity
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect
Net (Decrease) Increase in Cash and Cash Equivalents
Reduction in Total Residential Sector Budget
Reduction in Total Residential Sector Budget
Reduction in total residential sector budget
Entity Current Reporting Status
Fair Value, Inputs, Level 1 [Member]
Fair Value, Inputs, Level 1
Fair Value Inputs Level 1
Class of Stock [Domain]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets
Expected Long-term rate of return on plan assets
Defined Benefit Plan, Expected Long-term Return on Assets
With Effect From First March Two Thousand And Twenty Three [Member]
With Effect From First March Two Thousand And Twenty Three [Member]
Accounts Payable, Current, Total
Accounts Payable, Current
Accounts Payable
Financial Instrument [Axis]
Deferred Revenue Arrangement, by Type [Table]
Document Transition Report
Liability Class [Axis]
Commitments and Contingencies Disclosure [Abstract]
Defined Benefit Plan, Expected Return (Loss) on Plan Assets
Expected Return on Plan Assets
Increase (Decrease) in Regulatory Clause Revenue
Increase (decrease) in annual revenue
Increase Decrease Transfer Revenue Amount
Increase Decrease Transfer Revenue Amount
Transfer revenue amount
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]
3.43% Senior Notes, Due December 18, 2029
Current Liabilities:
Liabilities, Current [Abstract]
Total [Member]
Total [Member]
Total
Vesting Annual [Member]
Vesting Annual [Member]
Vesting Annually
Common Stock
Common Stock [Member]
Public Utilities Property Plant And Equipment Water
Public Utilities Property Plant And Equipment Water
Water
Retirement Plan Type [Axis]
Defined Benefit Plans Type Of Plans
Defined Benefit Plans Type Of Plans
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Derivatives
Proceeds from Lines of Credit, Total
Proceeds from Lines of Credit
Proceeds from lines of credit
Credit Facility [Domain]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent
State Income Taxes, net
State Income Taxes, net of Federal Income Tax Rate
Range [Domain]
Range [Domain]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Marketing And Outreach
Marketing And Outreach [Member]
Marketing And Outreach [Member]
Effective income tax rate reconciliation domestic income tax rate differential.
Effective Income Tax Rate Reconciliation Domestic Income Tax Rate Differential
Utility Plant Differences
Common Stock Including Additional Paid in Capital [Member]
Common Equity
Equity, Attributable to Parent [Abstract]
Stockholders' Equity:
AWC-NH And Abenaki [Member]
AWC-NH And Abenaki [Member]
Weighted Average Number of Shares Outstanding, Basic, Total
Weighted Average Number of Shares Outstanding, Basic
Weighted average number of shares outstanding used in the calculation of basic earnings per share
Weighted Average Common Shares Outstanding - Basic
Utilities Operating Expense, Maintenance and Operations, Total
Utilities Operating Expense, Maintenance and Operations
Operation and Maintenance
Finance Lease, Liability, to be Paid, Remainder of Fiscal Year
Rest of 2026
Second Solicitation
Second Solicitation [Member]
Second Solicitation Member
Assets [Abstract]
Percentage of Total Operating Revenues Including Cost Of Gas Supply
Percentage of Total Operating Revenues Including Cost Of Gas Supply
Percentage of total operating revenues including cost of gas supply
Track Two [Member]
Track Two [Member]
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]
4.04% Senior Notes, Due September 12, 2049
Entity Central Index Key
CIK
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Public Utilities, Approved Debt Capital Structure, Percentage
Percentage of approved return on equity, reflecting on debt
Percentage of approved return on equity, reflecting on debt
5.54% Senior Notes, Due 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 Twenty One Twenty Thirty Four [Member]
Receivables, Policy [Policy Text Block]
Exchange Gas Receivable
Agreement [Axis]
Agreement [Axis]
Site Contingency [Line Items]
Line of Credit Facility [Table]
Bangor
Bangor Natural Gas [Member]
Bangor Natural Gas
Bangor Natural Gas
Class of Stock [Line Items]
Other Liabilities, Current
Other Current Liabilities
Consolidation Items [Axis]
Current Fiscal Year End Date
Document Quarterly Report
Environmental Matters [Member]
Environmental Matters [Member]
Environmental Matters
Debt Instrument, Maturity Date
Debt instrument due date
Debt instrument maturity date
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Table]
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share Table
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Award Date [Domain]
Mayflower Wind Energy
Mayflower Wind energy [Member]
Mayflower Wind energy
Number of Customer
Number of Customer
Number of Customer
Operating Revenue
Operating Revenue
Operating Revenue
Business Combination, Acquisition-Related Cost, Expense
Acquisition amount
Public Utilities, Property, Plant and Equipment [Abstract]
Utility Plant:
Energy Supply Costs
Energy Supply Costs
Energy Supply Costs
Fair Value, Inputs, Level 2 [Member]
Fair Value, Inputs, Level 2
Fair Value Inputs Level 2
Senior Notes Five Point Eight Seven Percent Due April Thirty Two Thousand Forty One [Member]
Senior Notes Five Point Eight Seven Percent Due April Thirty Two Thousand Forty One [Member]
5.87% Senior Notes, Due April 30, 2041
Schedule of Regulatory Liabilities [Table Text Block]
Regulatory Liabilities
Imputed Interest On Operating Leases.
Imputed Interest On Operating Leases
Less: Interest
utl:GasRatePayersMember
Gas Rate Payers [Member]
Gas Ratepayers
Order [Axis]
Order [Axis]
Renewable Energy Portfolio Standards [Policy Text Block]
Renewable Energy Portfolio Standards [Policy Text Block]
Renewable Energy Portfolio Standards
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation
Cash Provided by Operating Activities
Entity Incorporation, State or Country Code
Earnings Per Share, Diluted, Total
Earnings Per Share, Diluted
Diluted
Earnings Per Common Share - Diluted
Sale of Stock, Number of Shares Issued in Transaction
Share sold under ATM program
Business Combination Consideration Transferred Cash And Cash Equivalents
Business Combination Consideration Transferred Cash And Cash Equivalents
Cash Paid for Acquisition
Transition Services Agreement Cost
Transition Services Agreement Cost
Transition Services Agreement Cost
Tax Jurisdiction Of Domicile Extensible Enumeration
Tax Jurisdiction of Domicile [Extensible Enumeration]
Operating Lease, Weighted Average Discount Rate, Percent
Operating lease, weighted average discount rate percentage
Net Income
Net Income Applicable to Common Shares
Granite State Gas Transmission Inc
Granite State Gas Transmission Inc [Member]
Granite State Gas Transmission Inc [Member]
Granite State Gas Transmission Inc
Energy Storage Systems 1
Energy Storage Systems 1
Energy Storage Systems 1
Energy storage systems
Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture, Total
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures
Stock Compensation Plans
Property, Plant and Equipment, Type [Domain]
Soliciation [Axis]
Soliciation Axis
Public Utilities Property Plant and Equipment related to Gas Operations.
Public Utilities Property Plant And Equipment Gas
Gas
Gas And Electric Utilities [Member]
Gas And Electric Utilities [Member]
Regulatory Asset [Member]
Regulatory Asset [Member]
Regulatory Assets
Regulatory Assets
Acquisition of Aquarion Water Companies Policy Text Block
Acquisition of Aquarion Water Companies Policy Text Block
Acquisition of Aquarion Water Companies
O2025 M10 Dividends [Member]
O2025 M10 Dividends [Member]
Fair Market Value Adjustment for Debt
Fair Market Value Adjustment for Debt
Less: Unamortized Debt Discount, net
Type of Restructuring [Domain]
Northern Utilities Inc [Member]
Northern Utilities Inc [Member]
Northern Utilities Inc
Northern Utilities Inc
O 2025 M4 Dividends [Member]
O 2025 M4 Dividends [Member]
O 2025 M4 Dividends [Member]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount
U.S. Federal Statutory Tax Rate
Cost of services margin
Cost of services margin
Cost of services margin
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
Restricted Stock Units Granted
Scenario [Domain]
Accounts Receivable, Allowance for Credit Loss, Ending Balance
Accounts Receivable, Allowance for Credit Loss, Beginning Balance
Allowance for Doubtful Accounts Receivable
Allowance for doubtful accounts
Allowance for Doubtful Accounts
Regulated Operation, Regulatory Liability [Table]
Equity Components [Axis]
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Investing Activities:
Regulatory Liability, Current
Less: Current Portion of Regulatory Liabilities
Regulatory Liabilities
Statement of Cash Flows [Abstract]
Fair Value Hierarchy and NAV [Domain]
Income Tax Disclosure [Abstract]
Retirement Benefits [Abstract]
Regulated Operation, Regulatory Asset [Table]
Schedule of Regulatory Assets [Table]
Dividends Declared [Table Text Block]
Schedule of Dividends Declared
Senior Notes Five Point Nine Nine Percent Due Twenty Forty Four [Member]
Senior Notes Five Point Nine Nine Percent Due Twenty Forty Four [Member]
5.99% Senior Note Due to 2044
Income Taxes [Member]
Income Taxes [Member]
Income Taxes
Stock Issued During Period, Shares, Restricted Stock Award, Gross
Performance restricted shares, shares awarded
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]
4.42% Senior Notes, Due October 15, 2044
Finance Lease, Liability, Noncurrent
Capital lease obligation, noncurrent
Other Noncurrent Liabilities (long-term portion)
DIVIDENDS DECLARED PER SHARE [Abstract]
Dividends Declared Per Share Abstract
Cash Deposits
Cash Deposits
Cash Deposits
Public Utilities, Inventory [Line Items]
Contract with Customer, Right to Recover Product, Total
Contract with Customer, Right to Recover Product
Recover costs of repairing damage
Obligations [Member]
Exchange Gas Obligation
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
Derivative Contract [Domain]
Hardship accounts in regulatory assets.
Hardship Accounts In Regulatory Assets
Hardship accounts in regulatory assets
Class of Stock [Axis]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Prior Service Cost Amortization
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).
Defined Benefit Plan Gross Periodic Benefit Cost
Sub-total
Program costs
Program Costs
Program Costs
Number of operating segments
Number of Operating Segments
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
With Effect From First Of November Two Thousand And Twenty Two [Member]
With Effect From First Of November Two Thousand And Twenty Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
Restricted stock that may be awarded in any one calendar year to any one participant
Increase Decrease In Deferred Revenue
Increase (Decrease) in Deferred Revenue
Proceeds from Issuance Initial Public Offering
Proceeds From Issuance Initial Public Offering
5.70% Senior Notes, Due July 8, 2030
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]
Weighted Average Cost Of Capital
Weighted Average Cost Of Capital
Weighted average cost of capital
Concentration Risk Benchmark [Domain]
Concentration Risk Benchmark [Domain]
Materials And Supplies [Member]
Materials and supplies.
Materials And Supplies
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
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares as of December 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number
Shares as of September 30, 2025
Line Of Credit Facility Commitment Amount
Line Of Credit Facility Commitment Amount
Loan commitment to fund an acquisition
Long-Term Debt, Current Maturities, Total
Long-term Debt, Current Maturities
Less: Current Portion
Long-Term Debt, Current Portion
Customer [Axis]
Award Date [Axis]
Short-Term Debt [Table]
Utility Plant
Public Utilities, Property, Plant and Equipment, Plant in Service
Group Two
Group Two [Member]
Group Two [Member]
Dividends, Common Stock, Total
Dividends, Common Stock
Dividends on Common Shares
Document Type
Document Type
Shares Issued, Shares, Share-Based Payment Arrangement, Forfeited
Forfeited Shares
Forfeited Shares
Defined Benefit Plan Disclosure [Line Items]
Cash and Cash Equivalents
Cash and Cash Equivalents, Policy [Policy Text Block]
Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]
Operating Activities:
Dividends Payable [Table]
Liabilities and Equity [Abstract]
LIABILITIES AND CAPITALIZATION:
Percentage Of Indebtedness To Net Capital.
Percentage Of Indebtedness To Net Capital
Total funded indebtedness as percentage of capitalization
Subsequent Event [Member]
Subsequent Event
Operating Income (Loss)
Operating Income
Goodwill, Acquired During Period
Acquisition of goodwill
Asset Retirement Obligations, Noncurrent, Total
Asset Retirement Obligations, Noncurrent
Cost of removal obligation
Cost of Removal Obligations
Sale of Stock, Price Per Share
Sale of stock, Average price per share
Billed and unbilled revenue.
Billed And Unbilled Revenue [Member]
Billed and Unbilled Revenue
Marketable Securities, Policy [Policy Text Block]
Investments in Marketable Securities
5.99% Senior Notes, Due August 21, 2034
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]
Acquisition of goodwill
Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Excluding Goodwill
Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Excluding Goodwill, Total
Number of Subsidiaries
Number of Subsidiaries.
Number of Subsidiaries | Entity
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]
3.58% Senior Secured Notes, Due September 15, 2040
Restricted Stock or Unit Expense
Share based compensation expense
Restricted stock and restricted stock units
Entity File Number
Actuarial Loss Amortization
Defined Benefit Plan, Amortization of Gain (Loss)
Actuarial Loss Amortization
Public Utilities, Approved Rate Increase (Decrease), Amount
Approved annual increase in rates
Significant Accounting Policies.
Significant Accounting Policies [Table]
Percentage of Weighted Average Cost Inventory
Retirement Plan Type [Domain]
Retirement Plan Type [Domain]
Tax Benefit Cost Recovery
Tax Benefit Cost Recovery
Tax Benefit Cost Recovery
Increase (Decrease) in Other Receivables
Exchange Gas Receivable
Exchange Gas Receivable
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]
Dividends Payable, Date of Record
Shareholder of Record Date
Retained Earnings [Member]
Retained Earnings
Description of the components and amounts included in Accrued Revenue.
Unbilled Accounts Receivable [Table Text Block]
Components of Accrued Revenue
6.31% Senior Notes, Due July 8, 2035
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]
Interest Payable, Current
Interest Payable
Interest Payable
Senior Notes Five Point Nine Nine Percent Due Twenty Thirty Four [Member]
Senior Notes Five Point Nine Nine Percent Due Twenty Thirty Four [Member]
Senior Notes Five Point Nine Nine Percent Due Twenty Thirty Four [Member]
Billing Status, Type [Axis]
Billing Status, Type [Axis]
Entity Registrant Name
Registrant Name
It represents Nature Of Operations Policy
Nature Of Operations [Policy Text Block]
Nature of Operations
Accounting Policies [Abstract]
Net Income
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest
Net Income
Profit Loss
Other Operating Segment [Member]
All Other Segments
Group Three [Member]
Group Three [Member]
Group Three
Weighted Average Cost Inventory Amount
Weighted average cost inventory amount
Gas Inventory
Entity Address, Address Line One
Noncash Investing Activity [Abstract]
Noncash Investing Activity [Abstract]
Non-cash Investing Activity:
Increase (Decrease) in Finished Goods and Work in Process Inventories
Reduction to construction work in progress.
Business Combination, Recognized Asset Acquired, Asset, Current
Business Combination, Recognized Asset Acquired, Asset, Current, Total
Acquisition of working capital
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
Liability Weighted Average Stock Price December 31, 2025
Time Restricted [Member]
Time Restricted [Member]
Time Restricted
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding, Number, Ending Balance
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Outstanding, Number, Beginning Balance
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number
Restricted stock units outstanding
Proceeds from (Repayments of) Short-Term Debt, Total
Proceeds from (Repayments of) Short-term Debt
Proceeds from Short-Term Debt, net
(Repayment of) Proceeds from Short-Term Debt, net
Assets, Current
Total Current Assets
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Net Periodic Benefit Cost Recognized
Natural Gas Liquids (NGL) [Member]
Liquefied Natural Gas & Other
Fair Value of Marketable Securities [Abstract]
Fair Value Of Marketable Securities Abstract
Program [Domain]
Program [Domain]
Segments [Axis]
Derivatives, Policy [Policy Text Block]
Derivatives
Commercial and industrial
Commercial And Industrial [Member]
Commercial & Industrial
Increase Decrease In Revenue
Increase Decrease In Revenue
Net increase to pretax income
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information:
Offshore Wind Energy
Offshore Energy [Member]
Offshore Wind Energy
Offshore Energy Member
Deferred Income Tax Expense (Benefit), Total
Deferred Income Tax Expense (Benefit)
Deferred Tax Provision
Entity Small Business
Long-Term Debt, Excluding Current Maturities, Total
Long-term Debt, Excluding Current Maturities
Total Long-Term Debt, Less Current Portion
Long-Term Debt, Less Current Portion
Finance Lease, Liability, to be Paid, after Year Five
2030-2034
2031-2035
MAINE
ME
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
Pension Plan [Member]
Pension Plans
Cash And Cash Equivalents Acquired
Cash And Cash Equivalents Acquired
Cash And Cash Equivalents Acquired
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options
Unrecognized share based compensation
Public Infrastructure Offering
Public Infrastructure Offering [Member]
Public Infrastructure Offering [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
Capital Lease Obligations Incurred
Payments on Capital Leases
Regulated Operation, Inventory [Table]
Soliciation [Domain]
Soliciation Domain
Preferred Stock, Dividend Rate, Percentage
Dividend rate
Significant Accounting Policies [Text Block]
Summary of Significant Accounting Policies
5.72% Senior Secured Notes, Due June 1, 2028
Senior Notes Five Point Seven Two Percent Due June One Two Thousand Twenty Eight [Member]
Senior Notes Five Point Seven Two Percent Due June One Two Thousand Twenty Eight [Member]
Accounts Receivable, after Allowance for Credit Loss, Current, Total
Accounts Receivable, Net, Current
Accounts Receivable, Net
Consolidation Items [Domain]
Percentage Of Prior Year Total Revenue
Percentage Of Prior Year Total Revenue
Percentage of prior year total revenue
Schedule of Long-term Debt Instruments [Table Text Block]
Details on Long Term Debt
Before June 1, 2022
Period one member.
Period One [Member]
Period 1
Finance Lease, Liability, to be Paid, Year Four
2029
2030
Energy [Axis]
Defined Benefit Plan, Plan Assets, Contributions by Employer
Employer Contributions
Environmental Restoration Costs [Member]
Environmental Restoration Costs
Earnings per common share
Derivative Asset
Derivative Asset
Derivative Asset, Total
Lessee, Operating Lease, Liability, to be Paid, Year Four
2029
2030
Regulated and Unregulated Operating Revenue, Total
Regulated and Unregulated Operating Revenue
Total Operating Revenues
Charges
Charges
Charges
Sale of Stock, Consideration Received Per Transaction
Gross proceeds
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
Subsequent Event Type [Axis]
Subsequent Event Type [Axis]
Operating Revenues [Abstract]
Operating Revenues Abstract
Equity [Abstract]
Product and Service [Domain]
Equity [Text Block]
Equity
Type of Reserve [Domain]
Rate adjustment mechanism revenue.
Rate Adjustment Mechanism Revenue [Member]
Rate Adjustment Mechanism Revenue
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]
Financing Activities:
Fair Value by Liability Class [Domain]
Receivables [Table]
Receivables Table
Average Participating Securities
Average Participating Securities
Less average participating securities
Total Noncurrent Liabilities
Liabilities, Noncurrent
New Hampshire
NH [Member]
Nh Member
Tranche A [Member]
Tranche A [Member]
Fitchburg Performance Base Rate Adjustment Gas [Member]
Fitchburg Performance Base Rate Adjustment Gas [Member]
Fitchburg Performance Base Rate Adjustment Gas
Public Utilities, Property, Plant and Equipment, Transmission and Distribution, Total
Public Utilities, Property, Plant and Equipment, Transmission and Distribution
Electric
Capital Lease Obligation [Abstract]
Capital Lease Obligation [Abstract]
Capital Lease Obligations:
Utility, Revenue and Expense Recognition, Policy [Policy Text Block]
Utility Revenue Recognition
Remuneration percentage.
Remuneration Percentage
Remuneration Percentage
Senior Notes One Point Two Hundred Ninty six Percent - Two Point Eight Hundred Sixty Four Due October One Two Thousand Thirty One - May One Two Thousand Fourty Five [Member]
Senior Notes One Point Two Hundred Ninty six Percent - Two Point Eight Hundred Sixty Four Due October One Two Thousand Thirty One - May One Two Thousand Fourty Five [Member]
1.296% - 2.864% Senior Notes, Due October 1, 2031 - May 1, 2045
Entity Tax Identification Number
Equity Issuance
Equity Issuance [Member]
Equity Issuance [Member]
Common Stock Equity
Common Stock Equity
Ending Balance
Beginning Balance
Total Common Stock Equity
Accounts Receivable [Member]
Accounts Receivable [member]
State Taxes Credit to Offset Future Taxes
State Taxes Credit to Offset Future Taxes
State Taxes Credit to Offset Future Taxes
After August 1, 2022
Period Three Member.
Period Three [Member]
Period 3
Derivative Instrument [Axis]
Equity Component [Domain]
Regulatory Asset [Axis]
Regulatory Assets Total Approved Recovery Amount
Regulatory Assets Total Approved Recovery Amount
Regulatory recovery amount
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Entity Address, City or Town
Tax Period [Domain]
Performance Restricted Shares [Member]
Performance Restricted Shares [Member]
Performance Restricted Shares
Capital Expenditures Incurred but Not yet Paid
Capital Expenditures Included in Accounts Payable
Income Taxes Paid, Net, Total
Income Tax Paid, after Refund Received
Income Taxes Paid
Stock Issued During Period, Value, New Issues
Issuance of Common Shares
Share Sold
Fitchburg Gas and Electric Light Company. [Member]
Fitchburg Gas And Electric Light Company [Member]
Fitchburg Gas and Electric Light Company
Fitchburg
Regulatory Liability [Domain]
Before August 1, 2022
Period two member.
Period Two [Member]
Period 2
Segments [Domain]
Third Amendment Credit Facility [Member]
Third Amendment Credit Facility
Third Amendment Credit Facility Member
Entity Common Stock, Shares Outstanding
Schedule of Debt [Table Text Block]
Borrowing Limits Amounts Outstanding and Amounts Available under Credit Facility
Marketable Securities [Table Text Block]
Fair Value of Marketable Securities
First Mortgage Bonds Five Point Six Nine Percent Senior Secured Notes Due August Twenty One Twenty Fifty Four [Member]
First Mortgage Bonds Five Point Six Nine Percent Senior Secured Notes Due August Twenty One Twenty Fifty Four [Member]
5.69% Senior Secured Notes, Due August 21, 2054
Dividends Payable [Line Items]
Entity [Domain]
Entity [Domain]
Regulatory Assets [Line Items]
Regulatory Assets [Line Items]
Business Combination, Recognized Liability Assumed, Long-Term Debt, Noncurrent
Acquisition long-term debt
Public Utilities, Requested Rate Increase (Decrease), Percentage
Benefit Plan Costs
Benefit Plan Costs [Member]
Benefit Plan Costs [Member]
Senior Notes Three Point Seventeen Percent Due June One Two Thousand Fifty One [Member]
Senior Notes Three Point Seventeen Percent Due June One Two Thousand Fifty One [Member]
3.17% Senior Notes, Due June 1, 2051
Liquified Natural Gas [Member]
Liquified Natural Gas [Member]
Liquified Natural Gas
Group Six [Member]
Group Six [Member]
Group Six
Unitil Energy Systems Inc
Unitil Energy Systems Inc
Unitil Energy Systems Inc [Member]
Unitil Energy Systems Inc
Statement [Table]
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
Restricted Stock Units Settled
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest
Income Before Income Taxes
Entity Shell Company
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation
Cash Used in Investing Activities
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
Aggregate Market Value
Statement [Line Items]
Business Combination, Recognized Asset Acquired, Asset, Noncurrent
Business Combination, Recognized Asset Acquired, Asset, Noncurrent, Total
Acquisition noncurrent assets
Table Text Block Supplement [Abstract]
Amount of capital expenditure approved by regulatory authority
Amount Of Capital Expenditure Approved By Regulatory Authority
Amount of capital expenditure approved by regulatory authority
Unbilled Revenues [Member]
Unbilled Revenues [member]
Unbilled Revenues
percent above present rates
Public Utility Rate Change Percentage
Public Utility Rate Change Percentage
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]
7.98% Notes, Due June 1, 2031
Other Current Asset [Member]
Other Current Asset [Member]
Group Five [Member]
Group Five [Member]
Group Five
Maximum [Member]
Maximum
Maximum [Member]
Schedule of Regulatory Assets [Table Text Block]
Regulatory Assets
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount
Other
Pro Forma Weighted Average Shares Outstanding, Diluted
Restricted stock and restricted stock units
Debt Disclosure [Abstract]
Finance Lease, Liability, to be Paid, Total
Finance Lease, Liability, Payment, Due
Total Payments
First Solicitation
First Solicitation [Member]
First Solicitation Member
Sale of Stock [Domain]
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
Statement of Financial Position Balance [Domain]
Statement of Financial Position Balance [Domain]
Add dilutive effect of:
Add dilutive effect of:
Accumulated deferred income taxes
Increase (Decrease) in Deferred Income Taxes
Accumulated deferred income taxes
Asset obtained to generate income or appreciate in value.
Investments Type Categorization [Domain]
Investments [Domain]
Approved commitments for purchasing assets
Approved commitments for purchasing assets
Approved commitments for purchasing assets
Concentration Risk Benchmark [Axis]
Concentration Risk Benchmark [Axis]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Statutory Federal Income Tax Rate
U.S. Federal Statutory Tax Rate Percent
Components of Exchange Gas Receivable [Abstract]
Components Of Exchange Gas Receivable Abstract
Power generation facility
Facility Power Capacity
Facility Power Capacity
Power generation facility
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Percent
Other, net
DRP [Member]
DRP [Member]
DRP
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]
4.32% Senior Notes, Due November 1, 2047
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
Avangrid Enterprises Inc
Avangrid Enterprises Inc [Member]
Avangrid Enterprises Inc [Member]
Assets, Current [Abstract]
Current Assets:
Debt Issuance Costs, Net
Repayments of debt
Finance Lease, Liability, Current
Capital lease obligation, current
Other Current Liabilities (current portion)
Period [Axis]
Period [Axis]
Period
Second Rate Step Adjustments [Member]
Second Rate Step Adjustments [Member]
Second Rate Step Adjustments
Sale of Stock, Consideration Received on Transaction
Net Proceeds
Fitchburg Performance Base Rate Adjustment Electric [Member]
Fitchburg Performance Base Rate Adjustment Electric [Member]
Fitchburg Performance Base Rate Adjustment Electric
Document Fiscal Year Focus
Petroleum Reserves [Axis]
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
Energy Marketing Contract Liabilities, Current
Energy Supply Obligations-Current
Energy Supply Obligations
Common Stock, Shares, Outstanding, Ending Balance
Common Stock, Shares, Outstanding, Beginning Balance
Common Stock, Shares, Outstanding
Common Equity Outstanding
Common stock, shares outstanding
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
Liability Weighted Average Stock Price March 31, 2026
Prime Rate [Member]
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]
3.70% Senior Notes, Due August 1, 2026
Components of Gas Inventory [Abstract]
Components Of Gas Inventory Abstract
Restructuring Type [Axis]
Income Tax Related Liabilities
Income tax related liabilities.
Income Tax Related Liabilities [Member]
Income Taxes
Financial Instruments [Domain]
Health care cost trend rate, assumed
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year
Health Care Cost Trend Rate Assumed for Next Year
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
Business Combination, Consideration Transferred
Business Combination, Consideration Transferred, Total
Acquired issued and outstanding shares
Natural Gas
Public Utilities, Inventory, Natural Gas [Member]
Forecast [Member]
Scenario Forecast
Group Seven [Member]
Group Seven [Member]
Group Seven
Secured Overnight Financing Rate (SOFR) [Member]
SOFR
Operating Lease, Liability, Noncurrent
Operating Lease Obligations
Operating Lease Obligations (long-term portion)
Increase Decrease Transfer Cost Amount
Increase Decrease Transfer Cost Amount
Increase in cost
Short-term Debt, Weighted Average Interest Rate, over Time
Weighted average interest rate on short term borrowings
Lessee, Operating Lease, Liability, to be Paid, Total
Lessee, Operating Lease, Liability, to be Paid
Total Payments
Common Stock Shares Issued Not Disclosed
Common Stock Shares Issued Not Disclosed
Lease Obligations
Lease Obligations [Member]
Lease Obligations [Member]
Security Exchange Name
New Accounting Pronouncements, Policy [Policy Text Block]
Recently Issued Pronouncements
Entity Address, State or Province
Equity ratio
Public Utilities, Requested Equity Capital Structure, Percentage
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]
5.74% Senior Notes, Due August 21, 2039
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
Share compensation recognition period
Total Reportable Segments [Member]
Total Reportable Segments [Member]
Total Reportable Segments
Accrual for Environmental Loss Contingencies, Charges to Expense for New Losses
Additions
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized
Restricted stock available for awards
O2026 M4 Dividends [Member]
O2026 M4 Dividends [Member]
Public Utilities, Policy [Policy Text Block]
Regulatory Accounting
Debt Instrument, Covenant Description
Percentage of capitalization
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
Allowance for Doubtful Accounts, Table.
Allowance For Doubtful Accounts [Table Text Block]
Allowance for Doubtful Accounts Included in Accounts Receivable Net
Supplemental Employee Retirement Plan [Member]
Supplemental Employee Retirement Plans, Defined Benefit
Supplemental Employee Retirement Plans, Defined Benefit
Power generation capacity
Power Generation Capacity
Power generation capacity
Operating Lease, Right-of-Use Asset
Operating Lease Right of Use Assets
The net change during the reporting period in deferred regulatory and other charges.
Change In Deferred Regulatory And Other Charges
Deferred Regulatory and Other Charges
Amendment Flag
Amendment
Common Stock Available For Future Sales
Common Stock Available for Future Sales
Future sales
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability
Right-of-Use Assets Obtained in Exchange for Lease Obligations
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Restricted Stock Units
Rate Adjustment Mechanisms
Rate Adjustment Mechanisms [Member]
Rate Adjustment Mechanisms & Other
ME [Member]
Maine
Me Member
Public Utilities, Requested Rate Increase (Decrease), Amount
Requested annual increase in rates
Receivables Billing Status [Domain]
Receivables Billing Status [Domain]
Debt Instrument [Axis]
Other (Income) Expense, Net
Other Nonoperating Income (Expense), Total
Other Nonoperating Income (Expense)
Other Expense (Income), Net
Tranche B [Member]
Tranche B [Member]
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
Period [Domain]
Period [Domain]
Period [Domain]
City Area Code
Dividends, Preferred Stock, Total
Dividends, Preferred Stock
Dividend declared
Schedule of Unvested Restricted Stock Units Roll Forward [Table Text Block]
Restricted Stock Units Issued
Schedule of Unvested Restricted Stock Units Roll Forward
Unitil Realty Corp Member
Unitil Realty Corp [Member]
Unitil Realty Corp Member
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item
Other, net
Energy Related Inventory, Natural Gas in Storage
Natural gas storage inventory
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
Accrual for Environmental Loss Contingencies, Total
Accrual for Environmental Loss Contingencies
Total Balance at End of Period
Total Balance at Beginning of Period
5.96% Senior Notes, Due July 2, 2053
Senior Notes Five Point Nine Six Percent Due july Two Twenty Fifty Three [Member]
Senior Notes Five Point Nine Six Percent Due july Two Twenty Fifty Three [Member]
Remaining Amortization Period.
Remaining Amortization Period
Amortization period for environmental costs
Proceeds from Issuance of Common Stock
Proceeds from Issuance of Common Stock
Proceeds from Issuance of Common Stock
3.78% Senior Notes, Due September 15, 2040
Senior Notes Three point Seventy percent Due September Fifteen Twenty Forty [Member]
Senior Notes Three Point Seventy Eight Percent Due September Fifteen Twenty Forty [Member]
3.78% Senior Notes, Due September 15, 2040
Accounts and Financing Receivables [Table]
Other deferred charges.
Other Deferred Charges [Member]
Other Deferred Charges
Operating Expenses [Abstract]
Operating Expenses
Asset Acquisition, Consideration Transferred, Contingent Consideration
Asset Acquisition Consideration Transferred Contingent Consideration
O2026M7DividendsMember
O2026 M7 Dividends [Member]
Weighted Average Number Of Share Outstanding Gross
Weighted Average Number Of Share Outstanding Gross
Weighted average common shares outstanding, gross
Date Paid (Payable)
Dividends Payable, Date to be Paid
Long-Term Purchase Commitment [Line Items]
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
Renewable Energy Portfolio Requirement [Member]
Renewable Energy Portfolio Requirement [Member]
Renewable Energy Portfolio Standards
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]
8.00% Senior Secured Notes, Due May 1, 2031
Pension and Other Postretirement Benefits Disclosure [Text Block]
Retirement Benefit Obligations
Common Stock, Par or Stated Value Per Share
Common stock per value
Legal Entity [Axis]
Legal Entity
Disclosure of Dividends Declared and Paid.
Disclosure Of Dividends Declared And Paid [Text Block]
Dividends Declared Per Share
Finance Lease, Liability, to be Paid, Year One
2027
Federal Funds Rate
Fed Funds Effective Rate Overnight Index Swap Rate [Member]
Electric and gas division.
Electric And Gas Division [Member]
Electric and Gas Division
Lessee, Leases [Policy Text Block]
Leases
Liabilities, Current
Total Current Liabilities
Commonwealth Wind [Member]
Commonwealth Wind [Member]
Commonwealth Wind
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
Liability as of December 31, 2025
Liability as of March 31, 2026
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations
Cash and Cash Equivalents at End of Period
Cash and Cash Equivalents at Beginning of Period
Segment Reporting [Text Block]
Segment Information
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Type of Arrangement and Non-arrangement Transactions [Axis]
Trading Symbol
Geographical [Axis]
Geographical [Axis]
Contractual Obligations [Member]
Contractual Obligations [Member]
Energy Supply and Other Rate Adjustment Mechanisms
Total Electric and Gas Operating Revenues
Revenue from Contract with Customer, Including Assessed Tax
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period
Restricted Stock Units Granted
Granted
Entity Emerging Growth Company
Dividends Payable, Date Declared
Declaration Date
Regulatory Liability [Axis]
Regulatory Liability
Regulatory Liability
Fitchburg Gas System Enhancement Program
Fitchburg Gas System Enhancement Program [Member]
Fitchburg Gas System Enhancement Program [Member]
Dividends [Axis]
Derivative, Fair Value, Net
Derivative, Fair Value, Net, Total
Fair value of derivative
Increased Number of Customers
Increased Number of Customers
Increased number of customers
Gain (Loss) on Contract Termination
Termination agreements
Long-term Debt, Gross
Total Long-Term Debt
Income Taxes [Table]
Income Taxes Table
Other Liabilities, Noncurrent
Other Noncurrent Liabilities
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization, Amount
Regulatory Amortization of Excess ADIT
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
5.96% Senior Notes, Due July 2, 2053
Other Regulatory Assets (Liabilities) [Member]
Other
Finance Lease, Liability, Total
Finance Lease, Liability
Total Capital Lease Obligations
Payments of Dividends, Total
Payments of Dividends
Dividends Paid
Regulated Operating Revenue
Regulated Operating Revenue
Regulated Operating Revenue, Total
O2026 M1 Dividends [Member]
O2026 M1 Dividends [Member]
Assets Under Capital Leases [Member]
Assets Under Capital Leases [Member]
Assets Under Capital Leases [Member]
Cover [Abstract]
Cover
Defined Benefit Plan, Interest Cost
Interest Cost
Interest Cost
Segment Reporting, Other Segment Item, Amount
Other Segment Expenses (Income)
Non current assets other than property plant and equipment.
Noncurrent Assets Other Than Property Plant And Equipment
Total Other Noncurrent Assets
Contractual Obligation [Line Items]
Contractual Obligation [Line Items]
Contractual Obligation [Line Items]
Accounts Receivable, before Allowance for Credit Loss, Current
AccountsReceivableGrossCurrent
Amount of Regulatory Costs Not yet Approved
Regulatory assets approved recovery amount
O 2025 M1 Dividends [Member]
O 2025 M1 Dividends [Member]
O 2025 M1 Dividends [Member]
It represents Allowance For Doubtful Accounts
Allowance For Doubtful Accounts [Policy Text Block]
Allowance for Doubtful Accounts
Public Utilities, Property, Plant and Equipment, Net
Net Utility Plant
Net Utility Plant
Equity Funds [Member]
Equity Funds
Equity Funds
Senior Unsecured Delayed Draw Term Loan Facility [Member]
Senior Unsecured Delayed Draw Term Loan Facility [Member]
Senior unsecured delayed draw term loan facility
Guarantees outstanding
Guarantees Outstanding
Guarantees Outstanding
Debtor-in-Possession Financing, Borrowings Outstanding
Borrowings outstanding
Operating Lease, Weighted Average Remaining Lease Term
Operating lease, weighted average remaining lease term
Third Solicitation
Third Solicitation [Member]
Third Solicitation
Electric Utilities [Member]
Electric Utilities [Member]
Deferred Storm Charges
Time Restricted Shares [Member]
Time Restricted Shares [Member]
Time Restricted Shares
Operating revenues.
Operating Revenues [Line Items]
Series 6 [Member]
Series Six [Member]
Series 6
Percentage Of Sales Volume
Percentage Of Sales Volume
Percentage of total sales volumes revenue subject to RDM
Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities:
Adjustments to Reconcile Net Income to Cash Provided by Operating Activities:
Cash and Cash Equivalents, at Carrying Value, Total
Cash and Cash Equivalent
Cash and Cash Equivalents
Electric Vehicle Supply Equipment
Electric Vehicle Supply Equipment [Member]
Electric Vehicle Supply Equipment [Member]
Major Storm Cost Reserve Recovery [Member]
Major Storm Cost Reserve Recovery [Member]
Major Storm Cost Reserve Recovery
Payments of Debt Issuance Costs
Long-Term Debt Issuance costs
Long-Term Debt Issuance costs
Schedule of Environmental Loss Contingencies by Site [Table Text Block]
Environmental Obligations Recognized by Company
Environmental Obligations Recognized by Company
Regulatory Assets [Abstract]
Regulatory Assets Abstract
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation
Cash Provided by Financing Activities
Mid Duration Storage
Mid-Duration Storage
Mid-Duration Storage
Performance Restricted [Member]
Performance Restricted [Member]
Performance Restricted
Segment Profit (Loss)
Net Income (Loss) Available to Common Stockholders, Basic, Total
Net Income (Loss) Available to Common Stockholders, Basic
Net Income Attributable to Common Shares
At The Market Offering [Member]
ATM
At The Market Offering [Member]
At-the-Market Equity Offering Program
Post-65 retirees
Post Sixty Five Retirees [Member]
Post sixty five retirees member.
Deferred Tax and Other Liabilities, Noncurrent
Deferred Income Taxes, Net
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period
Forfeitures under the stock plan
Entity Filer Category
Long-Term Purchase Commitment [Table]
Debt Instrument, Name [Domain]
Qualified Clean Energy
Qualified Clean Energy [Member]
Qualified Clean Energy
Qualified Clean Energy Member
Order Flow Fees
Order providing cost
Schedule of Assumptions Used [Table Text Block]
Key Weighted Average Assumptions Used in Determining Benefit Plan Costs and Obligations
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
Cancellations under the stock plan
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
Increase (Decrease) in Accounts Receivable
Accounts Receivable
Increase in Accounts Receivable
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
Revenue from Contract with Customer, Excluding Assessed Tax
Total Operating Revenues
Group Eight [Member]
Group Eight [Member]
Group Eight
Increase (Decrease) in Regulatory Liabilities
Regulatory Liabilities
Other Postretirement Benefits Plan [Member]
Retirement Benefits
Retirement Benefits
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Fully Vested, Number
Sharebased Compensation Arrangement By Sharebased Payment Award Equity Instruments Other Than Options Fully Vested Number
Ending Restricted Stock Units
Beginning Restricted Stock Units
Regulatory Liabilities [Line Items]
Regulatory Liabilities [Line Items]
Document Information [Line Items]
Document Information:
Segment Reporting [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Differences Between Provisions for Income Taxes and Provisions Calculated at Statutory Federal Tax Rate
Regulatory Liability, Noncurrent
Regulatory Liabilities – noncurrent
Regulatory Liabilities
Debt Securities, Trading, and Equity Securities, FV-NI, Total
Debt Securities, Trading, and Equity Securities, FV-NI
Investments in trading securities
Trading Securities
Entity Address, Postal Zip Code
Statement of Financial Position [Abstract]
Local Phone Number