Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Taxes [Abstract]
Income Taxes	‎ (16) Income Taxes: The following is a reconciliation of the provision for income taxes computed at the federal statutory rate to income taxes computed at the effective rates: Successor Predecessor For the eight For the four For the year For the year months ended months ended ended ended December 31, April 30, December 31, December 31, 2021 2021 2020 2019 Consolidated tax provision at federal statutory rate 21.0 % 21.0 % 21.0 % 21.0 % State income tax provisions, net of federal income tax benefit 3.1  0.5  21.7  2.6  Tax reserve adjustment 0.1  - (0.7) - Fresh start and reorganization adjustments - (24.9) - - Changes in certain deferred tax balances (8.2) - (35.8) (2.3) Interest expense deduction - - 30.7  - Restructuring cost - 0.3  (10.0) - Goodwill impairment - - - (11.8) Loss on disposal of Northwest Operations - - (9.1) - Share-based payments - - (0.2) (0.1) Federal research and development credit (0.4) - (0.5) - All other, net 1.6  - 0.1  - Effective tax rate 17.2 % (3.1)% 17.2 % 9.4 % Under ASC 740 – 270, income tax expense for the four months ended April 30, 2021, is based on the actual year to date effective tax rate for the first four months of the year inclusive of the impact of the fresh start and reorganization adjustments. Income tax expense for the eight months ended December 31, 2021 is based on the actual year to date effective tax rate for the successor period. CARES ActOn March 27, 2020, the CARES Act was enacted in response to the COVID-19 pandemic. The CARES Act contains numerous income tax provisions, such as relaxing limitations on the deductibility of interest and the use of net operating losses arising in taxable years beginning after December 31, 2017. The CARES Act has a number of beneficial tax provisions (e.g., deferral of the employer portion of social security taxes for the remainder of 2020, the ability to claim additional interest deductions, net operating loss carrybacks, and removal of the 80% usage limitation for post-2017 NOLs for tax years 2018, 2019 and 2020). Employers can defer payment of the employer’s share of the Social Security tax that they otherwise are responsible for paying on wages. The deferral applies to affected taxes normally required to be paid from March 27, 2020, through December 31, 2020. The deferred tax must be paid over the following two years, with half to be paid by December 31, 2021, and the other half to be paid by December 31, 2022. Under the program, Frontier deferred a total of $30 million and has repaid $30 million. Following CARES ACT, the consolidated Act as a second stimulus package was signed into law on 12/27/2020 with no impact to the Company. Other Tax ItemsAs of December 31, 2021, $13 million of expected income tax refunds are included in “Income taxes and other current assets” in the consolidated balance sheet. For the four months ended April 30, 2021 and the eight months ended December 31, 2021, we paid net federal and state income tax amounting to $9 million and $28 million, respectively. In 2020 and 2019, we paid net federal and state income tax totaling $8 million and $4 million, respectively. The components of the net deferred income tax liability (asset) are as follows: Successor Predecessor December 31, December 31, ($ in millions) 2021 2020 Deferred income tax liabilities: Property, plant, and equipment basis differences $ 859  $ 1,873  Intangibles 140  - Deferred revenue/expense (3) 44  Other, net 46  56  $ 1,042  $ 1,973  Deferred income tax assets: Pension liability $ 212  $ 308  Intangibles - 681  Tax operating loss carryforward 185  923  Employee benefits 151  207  Interest expense deduction limitation carryforward - 44  Accrued expenses 76  75  Lease obligations 75  83  Tax credit 4  40  Allowance for doubtful accounts 14  35  Other, net 30  17  747  2,413  Less: Valuation allowance (92) (783) Net deferred income tax asset 655  1,630  Net deferred income tax liability $ 387  $ 343  Our federal net operating loss carryforward as of December 31, 2021, is estimated at $312 million. The majority of the federal loss carryforward will begin to expire between 2036 and 2038, with $18 million carrying forward indefinitely, unless otherwise used. Our state tax operating loss carryforward as of December 31, 2021, is estimated at $1.8 billion. A portion of our state loss carryforward will continue to expire annually through 2041, unless otherwise used. Our federal research and development credit as of December 31, 2021, is estimated at $1 million. The federal research and development credit will begin to expire after 2041, unless otherwise used. Our various state credits as of December 31, 2021, are estimated at $3 million. The state credits will begin to expire after 2026, unless otherwise used. Frontier considered positive and negative evidence in regard to evaluating certain deferred tax assets during the second quarter of 2021, including the development of recent years of pre-tax book losses. As of December 31, 2021, Frontier has a valuation allowance of $92 million to reduce deferred tax assets to an amount more likely than not to be realized. This valuation allowance is related to state net operating losses, state tax credits, and the state impact from the federal limitation on interest expense deduction. In evaluating Frontier’s ability to realize its deferred tax assets, management considers whether it is more likely than not that some or all of the deferred tax assets will not be realized. Management also considered the projected reversal of deferred tax liabilities and projected future taxable income in making this assessment. Based upon this assessment, management believes it is more likely than not Frontier will realize the benefits of these deductible differences, net of valuation allowance. The provision (benefit) for federal and state income taxes, as well as the taxes charged or credited to equity of Frontier, includes amounts both payable currently and deferred for payment in future periods as indicated below: Successor Predecessor For the eight For the four For the year For the year months ended months ended ended ended December 31, April 30, December 31, December 31, ($ in millions)2021 2021 2020 2019 Income tax expense (benefit): Current: Federal$ - $ - $ (12) $ 1  State 8  12  19  7  Total Current 8  12  7  8  Deferred: Federal (84) (116) (84) (606) State 162  (32) (7) (13) Total Deferred 78  (148) (91) (619) Total income tax benefit 86  (136) (84) (611) Income taxes charged (credited) to equity of Frontier: Deferred income taxes (benefits) arising from the recognition of additional pension/OPEB liability 19  - 35  32  Total income taxes charged (credited) to equity of Frontier - - 35  32  Total income tax expense (benefit)$ 105  $ (136) $ (49) $ (579) U.S. GAAP requires applying a “more likely than not” threshold to the recognition and derecognition of uncertain tax positions either taken or expected to be taken in Frontier’s income tax returns. The total amount of our gross tax liability for tax positions that may not be sustained under a “more likely than not” threshold amounts to $1 million as of December 31, 2021, including immaterial interest. The amount of our uncertain tax positions, for which it is reasonably possible that the total amounts of unrecognized tax benefits will significantly increase or decrease during the next twelve months, and which would affect our effective tax rate is $0 million as of December 31, 2021. Frontier’s policy regarding the classification of interest and penalties is to include these amounts as a component of income tax expense. This treatment of interest and penalties is consistent with prior periods. We are subject to income tax examinations generally for the years 2018 forward for federal and 2016 forward for state filing jurisdictions. We also maintain uncertain tax positions in various state jurisdictions. The following table sets forth the changes in Frontier’s balance of unrecognized tax benefits: Successor Predecessor ($ in millions) December 31, April 30, December 31, 2021 2021 2020      Unrecognized tax benefits - beginning of period $  1  $ 16  $ 12  Gross increases - prior period tax positions - - 4  Gross increases - current period tax positions - (15) - Gross decreases - expired statute of limitations - - - Unrecognized tax benefits - end of period $ 1  $ 1  $ 16