Document and Entity Information [Abstract] Statement [Table] Statement [Line Items] Entity Registrant Name Document Quarterly Report Document Transition Report Entity Incorporation, State or Country Code Entity Central Index Key Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Document Type Amendment Flag Document Period End Date Entity Tax Identification Number Entity File Number Entity Address, Address Line One Entity Address, City or Town Entity Address, State or Province Entity Address, Postal Zip Code City Area Code Local Phone Number Title of 12(b) Security Security Exchange Name Trading Symbol Entity Current Reporting Status Entity Interactive Data Current Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Shell Company Entity Common Stock, Shares Outstanding Consolidated Balance Sheets [Abstract] Assets [Abstract] ASSETS Current assets: Current assets: Cash and cash equivalents Accounts Receivable, Net, Current Accounts receivable, net Accounts receivable, less allowances of $91 and $105, respectively Capitalized Contract Cost, Net, Current Contract acquisition costs Prepaid expenses Assets Held-for-sale, Not Part of Disposal Group, Current Assets held for sale Total assets held for sale Other Assets, Current Income taxes and other current assets Assets, Current Total current assets Property, plant and equipment, net Property, plant and equipment, net Goodwill Goodwill, Ending Balance Goodwill, Beginning Balance Other Intangible Assets, Net Net Carrying Amount Other intangibles, net Other Assets, Noncurrent Other assets Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND EQUITY (DEFICIT) Liabilities, Current [Abstract] Current liabilities: Long-term Debt, Current Maturities Less: Current Portion Long-term debt due within one year Accounts payable Contract With Customer Liability, Advanced Billings, Current Contract With Customer Liability, Advanced Billings, Current Advanced billings Accrued other taxes Accrued other taxes Interest and Dividends Payable, Current Accrued interest Pension and other postretirement benefits - current Pension and other postretirement benefits Liabilities Held-for-sale, Not Part of Disposal Group, Current Liabilities held for sale Total liabilities held for sale Other Liabilities, Current Other current liabilities Liabilities, Current Total current liabilities Deferred Tax Liabilities, Net, Noncurrent Deferred income taxes Pension and other postretirement benefits Other Liabilities, Noncurrent Other liabilities Long-term Debt, Excluding Current Maturities Total Long term debt Long-term debt Equity (Deficit): Common stock, $0.25 par value (1,750,000 authorized shares, 1,027,986 issued and 1,002,872 and 1,002,469 outstanding, respectively, at March 31, 2015 and December 31, 2014) Common stock, $0.25 par value (175,000 authorized shares, 106,025 issued and 105,370 and 105,536 outstanding, at September 30, 2019 and December 31, 2018, respectively) Additional paid-in capital Accumulated deficit Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss, net of tax Treasury Stock, Value Treasury common stock Stockholders' Equity Attributable to Parent Total equity (deficit) Liabilities and Equity Total liabilities and equity (deficit) Allowances for accounts receivable, current Preferred Stock, Shares Outstanding Preferred Stock Balance (in shares) Preferred Stock Balance (in shares) Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized (in shares) Common stock, shares issued (in shares) Common stock, shares outstanding (in shares) Common Stock Balance (in shares) Common Stock Balance (in shares) Consolidated Statements Of Operations [Abstract] Revenues Total revenue Revenue Operating expenses: Network Access Expenses Network Access Expenses Network access expenses Network Related Expenses includes certain expenses associated with the delivery of services to customers and the operation and maintenance of the network, such as facility rent, utilities, maintenance and other costs, as well as salaries, wages and related benefits associated with personnel who are responsible for the delivery of services, operation and maintenance of its communications network, but excludes depreciation and amortization. Network Related Expenses Network related expenses Selling, General and Administrative Expense Selling, general and administrative expenses Depreciation and amortization Depreciation and amortization Goodwill Impairment Goodwill impairment Goodwill impairment Gain on sale of Mohave partnership interest Loss on disposal of Northwest Operations Restructuring Costs Restructuring costs and other charges Operating Expenses Total operating expenses Operating Income (Loss) Operating income (loss) Nonoperating Income (Expense) Total investment and other income (loss), net Investment and other income (loss), net Pension Settlement Costs Pension Settlement Costs Pension settlement costs Loss on extinguishment of debt and debt exchanges Loss (gain) on extinguishment of debt Gain (loss) on extinguishment of debt Interest expense Income before income taxes Loss before income taxes Income Tax Expense (Benefit) Income tax expense (benefit) Income tax benefit Net loss Net income (loss) Net loss Net loss Less: Dividends on preferred stock Less: Dividends on preferred stock Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock but before participating securities; of income (loss) available to common shareholders. Net Income (Loss) Net Of Preferred Dividends Net loss attributable to Frontier common shareholders Earnings Per Share, Basic and Diluted Basic and diluted net loss per share attributable to Frontier common shareholders Weighted Average Number of Shares Outstanding, Basic and Diluted Total weighted average shares outstanding - basic and diluted Consolidated Statements Of Comprehensive Income (Loss) [Abstract] Net current-period other comprehensive income Other comprehensive income (loss), net of tax Net current-period other comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Consolidated Statements Of Equity (Deficit) [Abstract] Statement, Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid In Capital [Member] Additional Paid-in Capital [Member] Retained Earnings [Member] Accumulated Deficit [Member] Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Loss [Member] Treasury Stock [Member] Treasury Common Stock [Member] Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Balance Balance Cumulative Effect on Retained Earnings, Net of Tax Cumulative-effect adjustment Cumulative-effect adjustment, Net of tax Impact of adoption of new accounting principle Conversion of Stock, Shares Converted Conversion of preferred stock, shares converted Conversion of Stock, Amount Issued Conversion of preferred stock, amount issued Stock plans Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Stock plans (in shares) Amount of decrease in additional paid in capital (APIC) resulting from preferred dividends legally declared (or paid) in excess of retained earnings balance. Adjustments to Additional Paid in Capital, Preferred Dividends in Excess of Retained Earnings Dividends on preferred stock ($5.56 per share) Preferred Stock, Dividends Per Share, Declared Dividends on preferred stock per share Consolidated Statements Of Cash Flows [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows provided from (used by) operating activities: Adjustments to reconcile net loss to net cash provided from (used by) operating activities: Net Periodic Defined Benefits Expense (Reversal of Expense), Excluding Service Cost Component Pension settlement costs Stock-based compensation expense Amortization of Financing Costs Amortization of deferred financing costs Other adjustments Other adjustments Increase (Decrease) in Deferred Income Taxes Deferred income taxes Change in accounts receivable Change in accounts receivable Change in accounts payable and other liabilities Change in prepaid expenses, income taxes and other current assets Change in prepaid expenses, income taxes and other assets Net Cash Provided by (Used in) Operating Activities Net cash provided from operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows provided from (used by) investing activities: Payments to Acquire Productive Assets Capital expenditures Proceeds from the sale of real estate properties and the Frontier Secure Strategic Partners business Proceeds on sale of assets Payments for (Proceeds from) Other Investing Activities Other Net Cash Provided by (Used in) Investing Activities Net cash used by investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows provided from (used by) financing activities: Repayments of Long-term Debt Long-term debt payments Proceeds from long-term debt borrowings Proceeds from Lines of Credit Proceeds from revolving debt Repayments of Lines of Credit Repayment of revolving debt Payments of Financing Costs Financing costs paid Payments of Debt Extinguishment Costs Premium paid to retire debt Payments of Ordinary Dividends, Preferred Stock and Preference Stock Dividends paid on preferred stock Repayments of Long-term Capital Lease Obligations Finance lease obligation payments Repayment of customer advances for construction, distributions to noncontrolling interests and other Other Net Cash Provided by (Used in) Financing Activities Net cash provided from (used by) financing activities Decrease in cash, cash equivalents, and restricted cash Increase (Decrease) in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash at September 30, Cash, cash equivalents, and restricted cash at January 1, Supplemental cash flow information: Cash paid during the period for: [Abstract] Cash paid during the period for: [Abstract] Cash paid during the period for: Interest Income taxes Income tax payments, net Summary Of Significant Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Summary Of Significant Accounting Policies Recent Accounting Literature [Abstract] Accounting Changes and Error Corrections [Text Block] Recent Accounting Literature Revenue Recognition [Abstract] Revenue from Contract with Customer [Text Block] Revenue Recognition Accounts Receivable [Abstract] Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Accounts Receivable Property, Plant And Equipment [Abstract] Property, Plant and Equipment Disclosure [Text Block] Property, Plant And Equipment Goodwill And Other Intangibles [Abstract] Goodwill and Intangible Assets Disclosure [Text Block] Goodwill And Other Intangibles Planned Divestiture Of Northwest Operations [Abstract] Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Planned Divestiture Of Northwest Operations Fair Value Of Financial Instruments [Abstract] Fair Value Disclosures [Text Block] Fair Value Of Financial Instruments Long-Term Debt [Abstract] Debt Disclosure [Text Block] Long-Term Debt Restructuring Costs And Other Charges Restructuring and Related Activities Disclosure [Text Block] Restructuring Costs And Other Charges Leases [Abstract] Lease Disclosure [Text Block] Lease Disclosure [Text Block] Leases Investment And Other Income (Loss) [Abstract] Other Nonoperating Income and Expense [Text Block] Investment And Other Income (Loss) Income Taxes [Abstract] Income Tax Disclosure [Text Block] Income Taxes Net Loss Per Share [Abstract] Earnings Per Share [Text Block] Net Loss Per Share Stock Plans [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock Plans Comprehensive Income (Loss) [Abstract] Comprehensive Income (Loss) Note [Text Block] Comprehensive Income (Loss) Retirement Plans [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Retirement Plans Commitments And Contingencies [Abstract] Commitments and Contingencies Disclosure [Text Block] Commitments And Contingencies Basis of Presentation and Use of Estimates New Accounting Pronouncements, Policy [Policy Text Block] Accounting Changes Revenue Recognition Cash Equivalents Goodwill and Other Intangibles Lessee, Leases [Policy Text Block] Lease Accounting Assets Held-for-sale [Policy Text Block] Assets Held-for-sale [Policy Text Block] Assets Held for Sale Disaggregation of Revenue [Table Text Block] Disaggregation Of Revenue Contract with Customer, Asset and Liability [Table Text Block] Changes In Contract Assets And Contract Liabilities Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block] Performance Obligations, Revenue Accounts Receivable The tabular disclosure representing the activity relating to the valuation allowance for receivables due a company that are expected to be uncollectible. Activity in allowance for doubtful accounts [Table Text Block] Allowance For Doubtful Accounts Property, Plant and Equipment [Table Text Block] Property, Plant And Equipment, Net Schedule Of Depreciation Expense [Table Text Block] Schedule Of Depreciation Expense [Table Text Block] Schedule Of Depreciation Expense Components Of Goodwill By Reporting Units Goodwill Rollforward Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance, by either major class or business segment. Schedule Of Other Intangible Assets [Table Text Block] Components Of Other Intangibles Schedule of Amortization Expense [Table Text Block] Schedule of Amortization Expense [Table Text Block] Amortization Expense Assets Held For Sale Disclosure [Text Block] Components Of Held-For-Sale Assets And Liabilities Fair Value Of Long-Term Debt Schedule of Long-term Debt Instruments [Table Text Block] Long-Term Debt Senior Unsecured Debt Schedule of Maturities of Long-term Debt [Table Text Block] Debt Maturities by Year Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Restructuring Reserve Rollforward Schedule of Error Corrections and Prior Period Adjustments [Table Text Block] Effect Of The Adoption Of ASC 842 Lease, Cost [Table Text Block] Components Of Lease Cost Schedule of Lease Assets and Liabilities, Weighted-Average Lease Term and Discount Rate [Table Text Block] Schedule of Lease Assets and Liabilities, Weighted-Average Lease Term and Discount Rate [Table Text Block] Supplemental Balance Sheet Information Related To Leases Schedule Of Cash Flow, Supplemental Disclosures Related To Leases [Table Text Block] Schedule Of Cash Flow, Supplemental Disclosures Related To Leases [Table Text Block] Supplemental Cash Flow Information Related To Leases Lessee, Operating And Finance Lease, Liabilitys, Maturity [Table Text Block] Lessee, Operating And Finance Lease, Liabilitys, Maturity [Table Text Block] Maturity Analysis For Operating and Finance Lease Liabilities Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block] Maturity Analysis For Operating Leases From Customers Components Of Other Income, Net Components Of Investment And Other Income Reconciliation Of Provision For Income Taxes Calculation Of Net Income (Loss) Per Common Share LTIP Target Performance Shares Restricted Shares Outstanding Accumulated Other Comprehensive Loss, Net of Tax Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Reclassification Out of Accumulated Other Comprehensive Income Net Periodic Benefit Cost Number of Reportable Segments Number of reportable segments The amount of Universal Service Fund (USF) (primarily federal USF) surcharges collected from customers. Customer surcharges The amount of video franchise fees. Video Franchise Fees Video franchise fees Number of Operating Segments Number of operating segments Restricted Cash Restricted cash Capitalized Contract Cost, Amortization Period Expected customer life Straight Line Basis Funding Term Straight Line Basis Funding Term Funding term New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Cumulative Effect of New Accounting Principle in Period of Adoption Cumulative-effect adjustment, Net of tax Disaggregation of Revenue [Table] Disaggregation of Revenue [Line Items] Revenue from Contract with Customer, Excluding Assessed Tax Revenue from contracts with customers Subsidy and other regulatory revenue Subsidy and other regulatory revenue Subsidy revenue Lease Income Lease revenue Revenue, Remaining Performance Obligation Revenue from contracts with customers, performance obligation Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Performance obligation satisfaction period Contract with Customer, Asset, Net, Current Contract current assets, Ending balance Contract current assets, Beginning balance Contract with Customer, Asset, Reclassified to Receivable, Current Contract with Customer, Asset, Reclassified to Receivable, Current Contract current assets, Revenue recognized included in opening contract balance Contract With Customer, Asset, Contract Asset Initiation, Current Contract With Customer, Asset, Contract Asset Initiation, Current Contract current assets, Credits granted, excluding amounts recognized as revenue Contract With Customer, Asset, Reclassified Between Current And NonCurrent, Current Contract With Customer, Asset, Reclassified Between Current And NonCurrent, Current Contract current assets, Reclassified between Current and NonCurrent Contract With Customer, Asset, Reclassified To Held-for-Sale, Current Contract With Customer, Asset, Reclassified To Held-for-Sale, Current Contract current assets, Reclassified to held for sale Contract with Customer, Asset, Net, Noncurrent Contract current assets, Ending balance Contract noncurrent assets, Beginning balance Contract with Customer, Asset, Reclassified to Receivable, NonCurrent Contract with Customer, Asset, Reclassified to Receivable, NonCurrent Contract noncurrent assets, Revenue recognized included in opening contract balance Contract With Customer, Asset, Contract Asset Initiation, Noncurrent Contract With Customer, Asset, Contract Asset Initiation, Noncurrent Contract noncurrent assets, Credits granted, excluding amounts recognized as revenue Contract With Customer, Asset, Reclassified Between Current And NonCurrent, NonCurrent Contract With Customer, Asset, Reclassified Between Current And NonCurrent, NonCurrent Contract current assets, Reclassified between Current and NonCurrent Contract With Customer, Asset, Reclassified To Held-for-Sale, NonCurrent Contract With Customer, Asset, Reclassified To Held-for-Sale, NonCurrent Contract noncurrent assets, Reclassified to held for sale Contract with Customer, Liability, Current Contract current liabilities, Ending balance Contract current liabilities, Beginning balance Contract with Customer, Liability, Reclassified to Receivable, Current Contract with Customer, Liability, Reclassified to Receivable, Current Contract current liabilities, Revenue recognized included in opening contract balance Contract With Customer, Liability, Cash Received Excluding Amounts Recognized As Revenue, Current Contract With Customer, Liability, Cash Received Excluding Amounts Recognized As Revenue, Current Contract current liabilities, Cash received, excluding amounts recognized as revenue Contract With Customer, Liability, Reclassified Between Current And NonCurrent, Current Contract With Customer, Liability, Reclassified Between Current And NonCurrent, Current Contract current liabilities, Reclassified between Current and NonCurrent, NonCurrent Contract With Customer, Liability, Other, Current Contract With Customer, Liability, Other, Current Contract current liabilities, Other Contract With Customer, Liability, Reclassified To Held-for-Sale, Current Contract With Customer, Liability, Reclassified To Held-for-Sale, Current Contract current liabilities, Reclassified to held for sale Contract with Customer, Liability, Noncurrent Contract noncurrent liabilities, Ending balance Contract noncurrent liabilities, Beginning balance Contract with Customer, Liability, Revenue Recognized, Noncurrent Contract with Customer, Liability, Revenue Recognized, Noncurrent Contract noncurrent liabilities, Revenue recognized included in opening contract balance Contract With Customer Liability, Cash Received, Excluding Amounts Recognized As Revenue, Noncurrent Contract With Customer Liability, Cash Received, Excluding Amounts Recognized As Revenue, Noncurrent Contract noncurrent liabilities, Cash received, excluding amounts recognized as revenue Contract With Customer, Liability, Reclassified Between Current And NonCurrent, NonCurrent Contract With Customer, Liability, Reclassified Between Current And NonCurrent, NonCurrent Contract current liabilities, Reclassified between Current and NonCurrent Contract With Customer, Liability, Reclassified to Held for Sale, NonCurrent Contract With Customer, Liability, Reclassified to Held for Sale, NonCurrent Contract noncurrent liabilities, Reclassified to held for sale Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Retail and wholesale Other Receivables, Gross, Current Other Allowance for Doubtful Accounts Receivable Less: Allowance for doubtful accounts Bad debt expense Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Proceeds from Sale of Property, Plant, and Equipment Proceeds from sale of property Property, Plant, and Equipment, Carrying Value Property, Plant, and Equipment, Carrying Value Aggregate carrying value Gain (Loss) on Disposition of Property Plant Equipment Gain on sale of property Property, plant and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: Accumulated depreciation Depreciation expense Schedule of Goodwill [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite Lived Intangible Assets Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer Relationships [Member] Customer Base [Member] Goodwill [Line Items] Impairment Finite-Lived Intangible Asset, Useful Life Useful life Schedule of Indefinite-lived Intangible Assets by Segment [Table] Indefinite-lived Intangible Assets by Segment [Line Items] Goodwill, Reclassification Of Assets Held For Sale Goodwill, Reclassification Of Assets Held For Sale Reclassification as held for sale Schedule of Finite-Lived Intangible Assets by Major Class [Table] Trade Names [Member] Trade Name [Member] Finite-Lived Intangible Assets [Line Items] Other intangibles Gross Carrying Amount Finite-Lived Intangible Assets, Accumulated Amortization Accumulated Amortization Amortization expense Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan Disclosure [Line Items] Disposal Group, Including Discontinued Operation, Consideration Consideration amount Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net Accounts receivable, less allowances of $7 Disposal Group, Including Discontinued Operation, Prepaid and Other Assets, Current Prepaid expenses Disposal Group, Including Discontinued Operation, Acquisition Costs, Current Disposal Group, Including Discontinued Operation, Acquisition Costs, Current Contract acquisition costs Disposal Group, Including Discontinued Operation, Other Assets, Current Other current assets Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Property, plant and equipment, net Disposal Group, Including Discontinued Operation, Goodwill Goodwill Disposal Group, Including Discontinued Operation, Intangible Assets Other intangibles, net Disposal Group, Including Discontinued Operation, Other Assets Other assets Disposal Group, Including Discontinued Operation, Assets, Valuation Allowance Disposal Group, Including Discontinued Operation, Assets, Valuation Allowance Valuation allowance on assets held for sale Disposal Group, Including Discontinued Operation, Accounts Payable, Current Accounts payable Disposal Group, Including Discontinued Operation, Contract With Customer Liability, Advanced Billings, Current Disposal Group, Including Discontinued Operation, Contract With Customer Liability, Advanced Billings, Current Advanced billings Disposal Group, Including Discontinued Operation, Accrual for Taxes Other than Income Taxes, Current Disposal Group, Including Discontinued Operation, Accrual for Taxes Other than Income Taxes, Current Accrued other taxes Disposal Group, Including Discontinued Operation, Other Liabilities, Current Other current liabilities Disposal Group, Including Discontinued Operation, Pension and Other Postretirement and Postemployment Benefits Disposal Group, Including Discontinued Operation, Pension and Other Postretirement and Postemployment Benefits Pension and other postretirement benefits Disposal Group, Including Discontinued Operation, Other Liabilities Other liabilities Disposal Group, Including Discontinued Operation, Accounts Receivable, Allowance for Credit Loss, Current Disposal Group, Including Discontinued Operation, Accounts Receivable, Allowance for Credit Loss, Current Allowance for accounts receivable, classified as held for sale Disposal Group, Including Discontinued Operation, Pension Plan Benefit Obligation Pension liability Pension Asset Funding To Transfer Pension Asset Funding To Transfer Pension asset to transfer Pension Asset Funding To Transfer, Percent Pension Asset Funding To Transfer, Percent Percent of pension liability to transfer Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Portion At Fair Value Fair Value Disclosure [Member] Portion at Fair Value Measurement [Member] Carrying Reported Amount Fair Value Disclosure [Member] Carrying Amount [Member] Estimate Of Fair Value Fair Value Disclosure [Member] Fair Value [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term Debt, Unclassified [Abstract] Long-term debt [Abstract] Long-term Debt, Fair Value Total debt Schedule of Long-term Debt Instruments [Table] Statistical Measurement [Axis] Range [Member] Range [Domain] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Line of Credit Facility [Axis] Line Of Credit Facility Lender [Domain] Line of Credit Facility, Lender [Domain] 2015 JP Morgan Credit Agreement Jp Morgan2015 Credit Agreement [Member] JP Morgan Term Loan A [Member] JP Morgan Term Loan B Member Jp Morgan Term Loan B [Member] JP Morgan Term Loan B [Member] Information related to the 2016 COBANK Credit Agreement. Cobank Credit Agreement2016 [Member] CoBank Term Loan 2016 [Member] Items that relate to all JP Morgan Debt Instruments Jp Morgan Combined Credit Facility [Member] JP Morgan Combined Credit Facility [Member] JP Morgan Term Loan A and Revolver Member Jp Morgan Term Loan And Revolver [Member] JP Morgan Term Loan A and Revolver [Member] Revolving Credit Facility [Member] JP Morgan Revolving Credit Facility 2015 [Member] Letter Of Credit Two [Member] Letter Of Credit Two [Member] Letter Of Credit, July 2019 [Member] Long-term Debt, Type [Axis] Longterm Debt Type [Domain] Long-term Debt, Type [Domain] Description of a long-term debt. Senior Unsecured Debt [Member] Senior Unsecured Debt [Member] Debt Instrument [Axis] Debt Instrument Name [Domain] Debt Instrument, Name [Domain] Senior Note Three [Member] Senior Note Three [Member] Term Loan Due 3/31/2021 [Member] Senior Note Two [Member] Senior Note Two [Member] Debenture Due 2/1/2028 [Member] Senior Note Ten [Member] Senior Note Ten [Member] Senior Note Due 7/1/2021 [Member] Senior Note Eight [Member] Senior Note Eight [Member] Senior Note Due 3/15/2019 [Member] Senior Note March Twenty One Senior Note March Twenty One [Member] Senior Note Due 3/31/2021 [Member] Senior Note Thirty-One [Member] Senior Note Thirty One [Member] Term Loan Due 10/12/2021 [Member] Secured Revolving Debt Due Two [Member] Secured Revolving Debt Due Two [Member] Secured Revolving Debt Due 2/27/2024 [Member] Senior Notes Due 2020 [Member] Senior Notes Due2020 [Member] Senior Notes Due 2020 [Member] Senior Notes Due 2021 [Member] Senior Notes Due2021 [Member] Senior Notes Due 2021 [Member] Senior Notes One [Member] Senior Notes One [Member] Debenture Due 5/15/2027 [Member] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Base Rate [Member] Base Rate [Member] London Interbank Offered Rate L I B O R [Member] London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Line Items] Debt Instrument, Decrease, Repayments Payments and Retirements Payments to retire debt instruments Debt Instrument, Face Amount Debt instrument, face amount Debt instrument, maturity date Line of credit facility maximum borrowing capacity Debt Instrument, Acceleration Clause Number of days prior to the maturity date at which the maximum debt threshold must be met in order to not accelerate the debt. Days Prior To Maturity To Meet Threshold To Not Accelerate Debt Maximum debt threshold amount that much be reached in order to not accelerated the debt maturity. Maximum Debt Threshold To Not Accelerate Debt DebtInstrumentBasisSpreadOnVariableRate1 Interest rate margin The effective basis spread used to determine the effective interest rate. Debt Instrument, Interest Rate, Effective Basis Spread On Variable Rate Effective basis spread Debt Instrument, Interest Rate, Increase (Decrease) Increased interest rate Long-term Line of Credit Line of credit facility, current borrowings Interest Rate Gain (Loss) on Repurchase of Debt Instrument Loss on extinguishment of debt Long-term Debt, Ending Balance Long-term debt, ending balance Long-term debt, beginning balance Remaining outstanding principal Long-term debt Principal Outstanding New Borrowings Deferred Finance Costs, Net Less: Debt Issuance Cost Debt Instrument, Unamortized Discount (Premium), Net Less: Debt Discount Weighted average interest rate of long-term debt including debt issuance costs, premiums and or discounts. Weighted average interest rate of long-term debt Interest rate Senior Secured Debt [Member] Senior Secured Debt [Member] Senior Secured Debt [Member] Secured Debt, Unsecured Debt, Secured Subsidiary Debt, And Unsecured Subsidiary Debt [Member] Secured Debt Unsecured Debt Secured Subsidiary Debt And Unsecured Subsidiary Debt [Member] Secured Debt, Unsecured Debt, Secured Subsidiary Debt, And Unsecured Subsidiary Debt [Member] Senior Note Nine [Member] Senior Note Nine [Member] Senior Note Due 4/15/2020 [Member] SeniorNoteTwentyFiveMember Senior Note Twenty Six [Member] Senior Note Due 9/15/2020 [Member] Senior Note Twenty-Three [Member] Senior Note Twenty Three [Member] Senior Note Due 9/15/2021 [Member] Senior Note Eleven [Member] Senior Note Eleven [Member] Senior Note Due 4/15/2022 [Member] Senior Note Twenty Seven Senior Note Twenty Seven [Member] Senior Note Due 9/15/2022 [Member] Senior Note Twelve [Member] Senior Note Twelve [Member] Senior Note Due 1/15/2023 [Member] Senior Note Thirteen [Member] Senior Note Thirteen [Member] Senior Note Due 4/15/2024 [Member] Senior Note Twenty-Four [Member] Senior Note Twenty Four [Member] Senior Note Due 1/15/2025 [Member] Senior Note Twenty Eight Senior Note Twenty Eight [Member] Senior Note Due 9/15/2025 [Member] Senior Note Fourteen [Member] Senior Note Fourteen [Member] Debenture Due 11/1/2025 [Member] Senior Note Fifteen [Member] Senior Note Fifteen [Member] Debenture Due 8/15/2026 [Member] Senior Note Sixteen [Member] Senior Note Sixteen [Member] Senior Note Due 1/15/2027 [Member] Senior Note Seventeen [Member] Senior Note Seventeen [Member] Senior Note Due 8/15/2031 [Member] Senior Note Eighteen [Member] Senior Note Eighteen [Member] Debenture Due 10/1/2034 [Member] Senior Note Nineteen [Member] Senior Note Nineteen [Member] Debenture Due 7/1/2035 [Member] Senior Note Twenty [Member] Senior Note Twenty [Member] Debenture Due 10/1/2046 [Member] Senior Note Thirty [Member] Senior Note Thirty [Member] Debenture Due 11/15/2031 [Member] RUS Loan Contracts Due 1/3/2028 [Member] Rus Loan Contracts Due132028 [Member] RUS Loan Contracts Due 1/3/2028 [Member] Senior Note Twenty-One [Member] Senior Note Twenty One [Member] Debenture Due 2/15/2028 [Member] Senior Note Twenty-Two [Member] Senior Note Twenty Two [Member] Debenture Due 10/15/2029 [Member] Subsequent Event [Table] Subsequent Event [Line Items] Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year Principal Payments 2019 (remaining three months) Principal Payments 2020 Principal Payments 2021 Principal Payments 2022 Principal Payments 2023 Long-term Debt, Maturities, Repayments of Principal Five Fiscal Years Thereafter Long-term Debt, Maturities, Repayments of Principal Five Fiscal Years Thereafter Thereafter Schedule of Restructuring and Related Costs [Table] Restructuring Cost and Reserve [Line Items] Severance Costs Severance expense Transformation Costs Transformation Costs Transformation costs Restructuring Charges Restructuring charges Payments of Restructuring Reserve Costs Payments of Restructuring Reserve Costs Payment of restructuring costs Restructuring Reserve [Roll Forward] Restructuring Reserve Restructuring Reserve, Ending Balance Restructuring Reserve, Beginning Balance Other Restructuring Costs Other restructuring costs Payments for Restructuring Cash payments during the period Leases [Table] Leases [Table] Leases [Line Items] Leases [Line Items] Lessee, Operating And Finance Lease, Term of Contract Lessee, Operating And Finance Lease, Term of Contract Operating and finace lease terms, Lessee Lessee, Operating And Finance Lease, Option to Terminate, Period Lessee, Operating And Finance Lease, Option to Terminate, Period Option to terminate leases, Lessee Lessor, Operating Lease, Term of Contract Operator lease terms, Lessor Lessor, Operating Lease, Option to Terminate, Period Lessor, Operating Lease, Option to Terminate, Period Option to terminate leases, Lessor Schedule of Error Corrections and Prior Period Adjustment Restatement [Table] Error Corrections and Prior Period Adjustments Restatement [Line Items] Operating Lease, Liability Present value of lease liabilities Operating lease liabilities Operating lease liabilities Deferred Rent Deferred Rent Deferred rent Deferred Gain on Sale of Property Deferred gain on sale of property Tax Effect On Recognition Of Gain On The Sale Of Property Tax Effect On Recognition Of Gain On The Sale Of Property Tax effect on the gain of sale of property Operating Lease, Liability, Statement of Financial Position [Extensible List] Operating Lease, Right-of-Use Asset Operating right-of-use assets Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] Operating Lease, Liability, Current Current operating lease liabilities Operating Lease, Liability, Noncurrent Noncurrent operating lease liabilities Finance Lease, Right-of-Use Asset, Amortization Amortization of right-of-use assets Finance Lease, Interest Expense Interest on lease liabilities Finance Lease Cost Finance Lease Cost Finance lease cost Operating Lease, Cost Operating lease cost Sublease Income Sublease income Lease, Cost Total Lease cost Short-term Lease, Cost Short-term lease cost Variable Lease, Cost Variable lease cost Supplemental Balance Sheet Information Related To Leases [Line Items] Supplemental Balance Sheet Information Related To Leases [Line Items] Finance Lease, Right-of-Use Asset Finance right-of-use assets Finance Lease, Liability Finance lease liabilities Present value of lease liabilities Operating Lease, Weighted Average Remaining Lease Term Operating leases, Weighted-average remaining lease term Operating Lease, Weighted Average Discount Rate, Percent Operating leases, Weighted-average discount rate Finance Lease, Weighted Average Remaining Lease Term Finance lease, Weighted-average remaining lease term Finance Lease, Weighted Average Discount Rate, Percent Finance lease, Weighted-average discount rate Finance Lease, Liability, Current Finance lease liabilities, Current Finance Lease, Liability, Noncurrent Financed lease liabilities, Noncurrent Cash Provided By Operating Activities, Operating Leases Operating cash flows provided by operating leases Operating Lease, Payments Operating cash flows used by operating leases Finance Lease, Interest Payment on Liability Operating cash flows used by finance leases Finance Lease, Principal Payments Financing cash flows used by finance leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Right-of-use assets obtained in exchange for lease liabilities, Operating leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Right-of-use assets obtained in exchange for lease liabilities, Finance leases Lessee, Operating Lease, Liability, Payment, Due [Abstract] Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2019 (remaining three months) Lessee, Operating Lease, Liability, Payments, Due Year Two 2020 Lessee, Operating Lease, Liability, Payments, Due Year Three 2021 Lessee, Operating Lease, Liability, Payments, Due Year Four 2022 Lessee, Operating Lease, Liability, Payments, Due Year Five 2023 Lessee, Operating Lease, Liability, Payments, Due after Year Five Thereafter Lessee, Operating Lease, Liability, Payments, Due Total lease payments Lessee, Operating Lease, Liability,Imputed Interest Less: imputed interest Finance Lease, Liability, Payment, Due [Abstract] Finance Lease, Liability, Payments, Remainder of Fiscal Year 2019 (remaining three months) Finance Lease, Liability, Payments, Due Year Two 2020 Finance Lease, Liability, Payments, Due Year Three 2021 Finance Lease, Liability, Payments, Due Year Four 2022 Finance Lease, Liability, Payments, Due Year Five 2023 Finance Lease, Liability, Payments, Due after Year Five Thereafter Finance Lease, Liability, Payment, Due Total lease payments Finance Lease, Liability, Imputed Interest Less: imputed interest Lessor, Operating Lease, Payments to be Received, Remainder of Fiscal Year 2019 (remaining three months) Lessor, Operating Lease, Payments to be Received, Two Years 2020 Lessor, Operating Lease, Payments to be Received, Three Years 2021 Lessor, Operating Lease, Payments to be Received, Four Years 2022 Lessor, Operating Lease, Payments to be Received, Five Years 2023 Lessor, Operating Lease, Payments to be Received, Thereafter Thereafter Lessor, Operating Lease, Payments to be Received Total lease payments from customers Interest and dividend income Pension/OPEB costs Pension and OPEB benefit (costs) Other Nonoperating Income (Expense) All other, net Income Tax Contingency [Table] Income Tax Contingency [Line Items] Deferred Tax Assets, Valuation Allowance Valuation allowance Deferred Tax Assets, Valuation Allowance, Net Of Federal Benefit Deferred Tax Assets, Valuation Allowance, Net Of Federal Benefit Net of federal benefit Deferred Tax Assets, Net, Current Deferred Tax Assets, Net, Noncurrent Operating Loss Carryforwards Operating loss carryforward Equity Method Investment, Ownership Percentage Beneficial ownership Consolidated tax provision at federal statutory rate (in hundredths) State income tax provisions, net of federal income tax benefit (in hundredths) Effective income tax rate reconciliation, Remeasurement of certain deferred tax balances Effective income tax rate reconciliation, Remeasurement of certain deferred tax balances Remeasurement of certain deferred tax balances (in hundredths) The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to changes in tax reserves. Effective Income Tax Rate Reconciliation Tax Reserve Adjustment Tax reserve adjustment (in hundredths) The portion of the difference between the effective income tax rate and domestic federal statutory income tax rate attributable to changes in certain deferred tax balances. Effective Income Tax Rate Reconciliation, Change in Certain Deferred Tax Balances Changes in certain deferred tax balances (in hundredths) Goodwill impairment (in hundreths) Goodwill impairment (in hundreths) Effective Income Tax Rate Reconciliation, Nondeductible Expense, Gain (Loss) on Disposition of Business, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Gain (Loss) on Disposition of Business, Percent Loss on disposal of Northwest Operations (in hundreths) Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Shared-based payments (in hundreths) Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent Federal research and development tax credit (in hundreths) All other, net (in hundredths) Effective Income Tax Rate, Continuing Operations Effective tax rate (in hundredths) Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis] Antidilutive Securities Name [Domain] Antidilutive Securities, Name [Domain] An arrangement whereby a director is entitled to receive in the future, subject to vesting and other restrictions, a number of shares in the entity at a specified price, as defined in the agreement. Non Employee Directors Deferred Fee Plan And Equity Plan [Member] Non-Employee Directors' Deferred Fee Plan and Equity Plan [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Shares excluded from the computation of diluted earnings per share (in shares) Expense recognized during the period Basic Net loss attributable to Frontier common shareholders Total basic net loss attributable to Frontier common shareholders Net Income (Loss) Available to Common Stockholders, Diluted Total diluted net loss attributable to Frontier common shareholders Total weighted average shares and unvested restricted stock awards outstanding - basic (in shares) Weighted Average Number of Shares, Restricted Stock Less: Weighted average unvested restricted stock awards (in shares) Total weighted average shares outstanding - basic Total weighted average shares outstanding - basic (in shares) Basic net loss per share attributable to Frontier common shareholders Total weighted average shares outstanding - diluted Total weighted average shares outstanding - diluted (in shares) Diluted net loss per share attributable to Frontier common shareholders Diluted net loss per share attributable to Frontier common shareholders Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Award Type [Domain] Deferred Compensation Share Based Payments [Member] EIP Plans [Member] Stock Compensation Plan [Member] Performance Shares [Member] Restricted Stock [Member] Restricted Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of stock-based compensation plan under which grants were made and remained outstanding. Number of stock-based compensation plan under which grants were made Number Of Stock Based Compensation Plan Under Which Grants Were Not Made Number Of Stock Based Compensation Plan Under Which Grants Were Not Made Number of stock-based compensation plan under which grants were not made Shares authorized for grant under the plans (in shares) Shares available for grant under the plan (in shares) Shares granted (in shares) LTIP target performance shares granted, net (in shares) Restricted stock granted (in shares) Restricted Stock Restricted Stock Restricted stock vested Restricted stock vested, Aggregate fair value Restricted stock vested, fair value The total fair value of equity-based awards other than options outstanding as of the balance sheet date. Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Total Fair Value Balance at end of period, Aggregate fair value Balance at beginning of period, Aggregate fair value Fair value of unvested restricted stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Balance at end of period (in dollars per shares) Balance at beginning of period (in dollars per shares) Restriced stock, grant date fair value per share Remaining unrecognized compensation cost associated with unvested restricted stock awards Weighted average period over which unvested restricted stock awards unrecognized compensation cost is expected to be recognized (in years) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Balance at end of period (in shares) Balance at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Restricted stock vested (in shares) LTIP target performance shares earned (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Restricted stock forfeited (in shares) LTIP target performance shares forfeited (in shares) Restricted stock granted (in dollars per shares) Restricted stock vested (in dollars per shares) Restricted stock forfeited (in dollars per shares) Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Line Items] Other Comprehensive income (loss), before reclassifications, Net of Tax Other comprehensive income (loss) before reclassifications Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Amounts reclassified from accumulated other comprehensive loss to net loss Reclassifications, net of tax Deferred Tax Liabilities, Other Comprehensive Income Deferred tax items Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification Out Of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification Out Of Accumulated Other Comprehensive Income [Member] Reclassification out of Accumulated Other Comprehensive Income [Member] Retirement Plan Type [Axis] Retirement Plan Type [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Pension Plans Defined Benefit [Member] Pension Benefits [Member] Other Postretirement Benefit Plans Defined Benefit [Member] Postretirement Benefits Other Than Pensions (OPEB) [Member] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Reclassifications, pretax Reclassification from AOCI, Current Period, Tax Tax impact Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Capitalization of pension and OPEB expense related to engineering and plant construction Capitalization of pension and OPEB expense related to engineering and plant construction Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year Plan contributions required, 2019 Plan contributions Defined benefit plan, cash contributions by employer Plan assets Defined Benefit Plan, Fair Value of Plan Assets, Period Increase (Decrease) Increase in pension assets Percentage of increase in pension plan Percentage of increase in pension plan Actual return on plan assets Positive investment returns Benefit payments Service cost Interest cost on projected benefit obligation Defined Benefit Plan, Expected Return on Plan Assets Expected return on plan assets Amortization of prior service cost (credit) Defined Benefit Plan, Amortization of Gains (Losses) Amortization of unrecognized (gain) loss Defined benefit plan, Net periodic benefit cost, before settlement Defined benefit plan, Net periodic benefit cost, before settlement Net periodic pension benefit cost Defined Benefit Plan, Net Periodic Benefit Cost Net periodic benefit cost Commitments And Contingencies [Table] Commitments And Contingencies [Table] Commitments And Contingencies [Line Items] Commitments And Contingencies [Line Items] Regulatory Required Expenditures Capital expenditures anticipated [Abstract] Regulatory Commitments [Abstract] Annual support offered by the Federal Communications Commission Annual support offered by the Federal Communications Commission Number of households to be serviced under regulatory funded programs Number of households to be serviced under regulatory funded programs Number of States in our Territory Number of States in our Territory Adjustments for New Accounting Pronouncements [Axis] Type Of Adoption [Member] Type of Adoption [Domain] New Accounting Pronouncement [Member] Adjustments for New Accounting Pronouncement [Member] Accounting Standards Update201602 [Member] Accounting Standards Update 2016-02 [Member] Accounting Standards Update201409 [Member] Accounting Standards Update 2014-09 [Member] Accounting Standards Update201802 [Member] Accounting Standards Update 2018-02 [Member] Preferred Stock [Member] Preferred Stock [Member] Accounting Standards Update201811 [Member] Accounting Standards Update 2018-11 [Member] Product and Service [Axis] Products And Services [Domain] Product and Service [Domain] Data And Internet Services [Member] Data And Internet Services [Member] Data And Internet Services [Member] Voice Services [Member] Voice Services [Member] Voice Services [Member] Video [Member] Video [Member] Video Services [Member] Other Customer Revenues [Member] Other Customer Revenues [Member] Other [Member] Statement, Business Segments [Axis] Segment [Domain] Segment [Domain] Consumer Portfolio Segment [Member] Consumer [Member] Commercial Portfolio Segment [Member] Commercial [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Property, Plant and Equipment, Type [Axis] Property Plant And Equipment Type [Domain] Property, Plant and Equipment, Type [Domain] Towers [Member] Towers [Member] Towers [Member] Royalty Agreements [Member] Royalty Agreement [Member] Secured Debt [Member] Secured Debt [Member] Unsecured Debt [Member] Unsecured Debt [Member] Secured Subsidiary Debenture [Member] Secured Subsidiary Debenture [Member] Secured Subsidiary Debt [Member] Unsecured Subsidiary Debt [Member] Unsecured Subsidiary Debt [Member] Unsecured Subsidiary Debt [Member] First Lien Notes Due 2027 [Member] First Lien Notes Due2027 [Member] First Lien Notes Due 4/1/2027 [Member] Second Lien Notes Due 4/1/2026 [Member] Second Lien Notes Due412026 [Member] Second Lien Notes Due 4/1/2026 [Member] Senior Debt Thirty Two Member Senior Debt Thirty Two [Member] Term Loan Due 6/15/2024 [Member] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Letter Of Credit [Member] Letter of Credit [Member] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Parent Company [Member] Parent Company [Member] Subsidiaries [Member] Subsidiaries [Member] Revolver One [Member] Revolver One [Member] Revolver Due 2/27/2024 [Member] IDRB due 5/1/2030 [Member] Idrb Due512030 [Member] IDRB Due 5/1/2030 [Member] Equipment Financings [Member] Equipment Financings [Member] Equipment Financings [Member] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Current Liabilities [Member] Other Current Liabilities [Member] Other Noncurrent Liabilities [Member] Other Noncurrent Liabilities [Member] Deferred Tax Liabilities Noncurrent [Member] Deferred Tax Liabilities Noncurrent [Member] Deferred Tax Liabilities Noncurrent [Member] Restatement [Axis] Restatement [Domain] Restatement [Domain] Scenario Previously Reported [Member] Previously Reported [Member] Geographical [Axis] Segment Geographical [Domain] Geographical [Domain] Washington, Oregon, Idaho, And Montana [Member] Washington Oregon Idaho And Montana [Member] Washington, Oregon, Idaho, And Montana [Member] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Internal Revenue Service I R S [Member] Internal Revenue Service (IRS) [Member] Investment, Name [Axis] Equity Method Investee Name [Domain] Investment, Name [Domain] Shareholder's Right Plan [Member] Shareholder S Right Plan [Member] Shareholder's Right Plan [Member] Deferred Taxes On Pension And OPEB Costs [Member] Deferred Taxes On Pension And O P E B Costs [Member] Deferred Taxes On Pension And OPEB Costs [Member] Accumulated Defined Benefit Plans Adjustment [Member] Amortization Of Defined Benefit Cost Items [Member] Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member] Prior-Service Credits (Costs) [Member] Accumulated Defined Benefit Plans Adjustment Net Unamortized Gain Loss [Member] Actuarial Gains (Losses) [Member] Accumulated Defined Benefit Plans Adjustment, Net Actuarial Loss for Pension Settlement Costs Member Accumulated Defined Benefit Plans Adjustment Net Actuarial Loss For Pension Settlement Costs [Member] Pension Settlement Cost [Member] Other Commitments [Axis] Other Commitments [Domain] Other Commitments [Domain] CAF II [ Member] Caf I I [Member] CAF Phase II [ Member] Northwest Operations [Member] Northwest Operations [Member] Northwest Operations [Member]