Transactions with Related Parties - Summary of Management Fee Expense (Detail) - PNMAC Capital Management LLC [Member] - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Related Party Transaction [Line Items] | ||||
| Total management fee incurred during the period | $ 6,869 | $ 7,133 | $ 13,881 | $ 14,321 |
| Average shareholders' equity amounts used to calculate base management fee expense | 1,836,690 | 1,912,522 | 1,866,238 | 1,919,962 |
| Base management fee [Member] | ||||
| Related Party Transaction [Line Items] | ||||
| Total management fee incurred during the period | 6,869 | 7,133 | 13,881 | 14,321 |
| Performance incentive fee [Member] | ||||
| Related Party Transaction [Line Items] | ||||
| Total management fee incurred during the period | $ 0 | $ 0 | $ 0 | $ 0 |