Mortgage-Backed Securities - Summary of Investment in Mortgage Backed Securities Activity (Detail) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Mortgage Backed Securities [Line Items] | ||
| Balance at beginning of quarter | $ 4,452,859 | |
| Changes in fair value included in income arising from: | ||
| Balance at end of quarter | 3,765,539 | |
| Mortgage Backed Securities [Member] | ||
| Mortgage Backed Securities [Line Items] | ||
| Balance at beginning of quarter | 4,452,859 | $ 4,063,706 |
| Purchases | 4,000 | 0 |
| Sales | (477,360) | 0 |
| Repayments | (188,953) | (102,769) |
| Changes in fair value included in income arising from: | ||
| Amortization and accrual of net purchase premiums and discounts , net | 8,400 | 10,070 |
| Valuation adjustments, net | (33,407) | 64,855 |
| Total changes in fair value included in income | (25,007) | 74,925 |
| Balance at end of quarter | $ 3,765,539 | $ 4,035,862 |