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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jun. 30, 2018 | Dec. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2011
Tax Credit Carryforward [Line Items] |  |  |  |
Deferred Tax Liabilities, Net |  | $ 24,000 | $ 32,000 |
Impact of AMT Repeal on Current Taxes | $ 29,581 |  |  |
Net Impact of New Tax Law | $ 1,886 |  |  |
NOL allocated amount |  | 3,639,000 |  | $ 3,440,000
AFG [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
NOL allocated amount |  | 1,457,000 |  |
U. S. Federal Net Operating Tax [Member] |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
NOL allocated amount |  | $ 3,639,000 |  |
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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