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Income Taxes Income Taxes - NOL Usage Table (Details) - USD ($) $ in Millions | 3 Months Ended | 87 Months Ended |
--- | --- | --- | ---
Mar. 31, 2020 | Dec. 31, 2018 | Sep. 30, 2011
Net Income Loss Reconciliation [Line Items] |  |  |
AACNetTaxableIncome |  | $ 1,508 |
Remaining Net Operating Loss Carryforward, Amount | $ 2,142 |  |
Tolling Payment Payable to AFG, Gross | $ 28 |  |
NOL allocated amount |  |  | $ 3,650
Tier C Tolling Payments Payable to IRS | 12.50% |  |
Tier D Tolling Payments Payable to IRS | 17.50% |  |
Ambac Assurance [Member] |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |
AACNetTaxableIncome | $ 172 |  |
NOL allocated amount | 2,457 |  |
Operating Loss Generated in Current Year | 143 |  |
Afg [Member] |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |
NOL allocated amount | 1,246 |  |
Operating Loss Generated in Current Year | 168 |  |
Domestic Tax Authority [Member] |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |
NOL allocated amount | $ 3,703 |  |
Minimum [Member] |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029 |  |
Maximum [Member] |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2040 |  |

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