Mortgage-Backed Securities - Summary of Investment in Mortgage Backed Securities Activity (Detail) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Mortgage Backed Securities [Line Items] | ||||
| Balance at beginning of period | $ 4,452,859 | |||
| Changes in fair value included in income arising from: | ||||
| Balance at end of period | $ 4,075,660 | 4,075,660 | ||
| Mortgage Backed Securities [Member] | ||||
| Mortgage Backed Securities [Line Items] | ||||
| Balance at beginning of period | 3,765,539 | $ 4,035,862 | 4,452,859 | $ 4,063,706 |
| Purchases | 486,407 | 37,082 | 490,407 | 37,082 |
| Sales | 0 | 0 | (477,360) | 0 |
| Repayments | (186,316) | (128,045) | (375,269) | (230,814) |
| Changes in fair value included in income arising from: | ||||
| Amortization and accrual of net purchase premiums and discounts , net | 9,604 | 7,582 | 18,004 | 17,652 |
| Valuation adjustments, net | 426 | 14,564 | (32,981) | 79,419 |
| Total changes in fair value included in income | 10,030 | 22,146 | (14,977) | 97,071 |
| Balance at end of period | $ 4,075,660 | $ 3,967,045 | $ 4,075,660 | $ 3,967,045 |