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Summary of Net Gain (Loss) Included in Consolidated Statements of Operations for Changes in Fair Value of Derivatives and Periodic Net Interest Settlements Under Derivatives (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Net gain (loss) for changes in fair value and net settlements of derivatives | $ 0 | $ 2,553 | $ 0 | $ 9,093 |
Interest Rate Swap |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Net gain (loss) for changes in fair value and net settlements of derivatives |  | 500 | 0 | 3,000 | $ 0
Interest Rate Swap | Net Realized Investment Gains (Losses) |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Net gain (loss) for changes in fair value and net settlements of derivatives | $ 0 | $ 2,553 | $ 0 | $ 9,093 |

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