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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2020 | Sep. 30, 2011
Tax Credit Carryforward [Line Items] |  |
NOL allocated amount |  | $ 3,650
Afg [Member] |  |
Tax Credit Carryforward [Line Items] |  |
NOL allocated amount | $ 1,246 |
Minimum [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 |

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