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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2019 | Dec. 31, 2017 | Dec. 31, 2018 | Sep. 30, 2011
Tax Credit Carryforward [Line Items] |  |  |  |
Deferred Tax Liabilities, Net | $ 32,000 |  | $ 40,000 |
Tolling Payment Payable to AFG | 147,000 |  |  |
Impact of AMT Repeal on Current Taxes |  | $ 29,581 |  |
Impact of new Tax Law on Deferred Taxes |  | 31,418 |  |
Net Impact of New Tax Law |  | 1,886 |  |
Unrecognized Tax Benefits, Interest on Income Taxes Accrued | 0 | $ 0 | $ 0 |
NOL allocated amount | 3,535,000 |  |  | $ 3,650,000
AFG [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
NOL allocated amount | 1,250,000 |  |  |
U. S. Federal Net Operating Tax [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
NOL allocated amount | $ 3,535,000 |  |  |
Minimum [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029 |  |  |
Minimum [Member] | AFG [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2029 |  |  |
Maximum [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Operating Loss Carryforwards, Expiration Date | Dec. 31, 2040 |  |  |
Maximum [Member] | AFG [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Operating Loss Carryforwards, Expiration Date | Jan. 01, 2034 |  |  |

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