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Summary of Significant Policies - Unaudited Pro Forma Information (Detail) - USD ($) |  | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2020 | Dec. 25, 2020 | Mar. 27, 2020
Accounting Policies [Line Items] |  |  |
Dividends paid | $ 400,000,000 | $ 400,000,000 |
Proceeds from initial public offering, net of underwriting discounts and other offering costs | 300,000,000 | $ 321,425,000 |
Pro forma adjustments to reflect the Common Stock Repurchases |  | 2,068,274 | 2,068,234
Term Loan Facility | Credit Suisse AG Cayman Islands Branch |  |  |
Accounting Policies [Line Items] |  |  |
Maximum borrowing capacity | $ 325,000,000 |  |
Class A common stock and Class L common stock |  |  |
Accounting Policies [Line Items] |  |  |
Number of Common Stock Conversion |  | 166,500,000 | 166,499,760

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