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Related Party Transactions - Summary of Related Party Carrying Value of Investments In Advances (Parenthetical) (Detail) - USD ($) $ in Millions | Oct. 18, 2023 | Sep. 30, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Oct. 07, 2021
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Related Party Transaction [Line Items] |  |  |  |  |
Principal borrowing amount |  |  |  |  | $ 700.0
SSGT III |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Principal borrowing amount |  | $ 9.5 | $ 17.5 |  |
SST VI Mezzanine Loan |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Principal borrowing amount |  |  | $ 20.0 | $ 38.2 |
SSGT III Mezzanine Loan |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Principal borrowing amount | $ 8.0 |  |  |  |

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