Mortgage-Backed Securities - Summary of Investment in Mortgage Backed Securities Activity (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Mortgage Backed Securities [Line Items] | ||||
| Balance at beginning of period | $ 4,063,706 | |||
| Changes in fair value included in income arising from: | ||||
| Balance at end of period | $ 3,967,045 | 3,967,045 | ||
| Mortgage Backed Securities [Member] | ||||
| Mortgage Backed Securities [Line Items] | ||||
| Balance at beginning of period | 4,035,862 | $ 3,949,678 | 4,063,706 | $ 4,836,292 |
| Purchases | 37,082 | 239,875 | 37,082 | 399,460 |
| Sales | 0 | 0 | 0 | (941,340) |
| Repayments | (128,045) | (92,877) | (230,814) | (162,629) |
| Changes in fair value included in income arising from: | ||||
| Accrual of net purchase premiums and discounts | 7,582 | 6,586 | 17,652 | 9,677 |
| Valuation adjustments, net | 14,564 | (34,925) | 79,419 | (73,123) |
| Total changes in fair value included in income | 22,146 | (28,339) | 97,071 | (63,446) |
| Balance at end of period | $ 3,967,045 | $ 4,068,337 | $ 3,967,045 | $ 4,068,337 |