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Income Taxes Income Taxes - NOL Usage Table (Details) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2011
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
Impact of AMT Repeal on Current Taxes |  | $ 29,581 |  |  |
Change in Impact of AMT Repeal on Current Taxes | $ 1,902 |  |  |  |
AMT Related to Filing of 2017 Tax Return |  | 5,536 |  |  |
AMT Receivable Resulting from TCJA |  |  |  | $ 37,019 |
Net Impact of New Tax Law |  | $ 1,886 |  |  |
NOL allocated amount |  |  | $ 3,639,000 |  | $ 3,440,000
Amount of NOL Reallocated from AAC to AFG |  |  | 210,000 |  |
Tolling Payments Paid by AAC to AFG |  |  | 28,000 |  |
AFG [Member] |  |  |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
NOL allocated amount |  |  | $ 1,457,000 |  |
Minimum [Member] |  |  |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
Operating Loss Carryforwards, Expiration Date |  |  | Dec. 31, 2029 |  |
Minimum [Member] | Ambac Assurance [Member] |  |  |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
Operating Loss Carryforwards, Expiration Date |  |  | Dec. 31, 2029 |  |
Minimum [Member] | AFG [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 |  |
Potential Tolling Payment From AAC to IRS |  |  | $ 8,000 |  |
Maximum [Member] | Ambac Assurance [Member] |  |  |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
Operating Loss Carryforwards, Expiration Date |  |  | Dec. 31, 2040 |  |
Maximum [Member] | AFG [Member] |  |  |  |  |
Net Income Loss Reconciliation [Line Items] |  |  |  |  |
Operating Loss Carryforwards, Expiration Date |  |  | Jan. 01, 2034 |  |

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