| **INVESTMENT SECURITIES - Gross Unrealized Loss and Fair Value of AFS Debt Securities (Details) - USD ($) $ in Thousands** | Dec. 31, 2023 | Dec. 31, 2022 |
|----------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | $ 21,066      | $ 3,174,326   |
| 12 months or longer                                                                                                        | 5,751,599     | 3,827,491     |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | (169)         | (261,473)     |
| 12 months or longer                                                                                                        | (922,254)     | (662,667)     |
| U.S. Treasury securities                                                                                                   |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 6,992         | 212,990       |
| 12 months or longer                                                                                                        | 0             | 0             |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | 0             | (2,481)       |
| 12 months or longer                                                                                                        | 0             | 0             |
| Corporate debt securities                                                                                                  |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 7,325         | 365,702       |
| 12 months or longer                                                                                                        | 13            | 0             |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | (1)           | (968)         |
| 12 months or longer                                                                                                        | 0             | 0             |
| ABS                                                                                                                        |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 6,749         | 269,158       |
| 12 months or longer                                                                                                        | 402,325       | 221,508       |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | (168)         | (7,551)       |
| 12 months or longer                                                                                                        | (1,751)       | (6,409)       |
| GNMA - Residential                                                                                                         |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 0             | 1,269,413     |
| 12 months or longer                                                                                                        | 2,792,843     | 1,811,609     |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | 0             | (144,616)     |
| 12 months or longer                                                                                                        | (394,756)     | (258,978)     |
| GNMA - Commercial                                                                                                          |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 0             | 149,717       |
| 12 months or longer                                                                                                        | 518,210       | 425,711       |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | 0             | (20,243)      |
| 12 months or longer                                                                                                        | (141,672)     | (84,469)      |
| FHLMC and FNMA - Residential                                                                                               |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 0             | 856,047       |
| 12 months or longer                                                                                                        | 1,949,320     | 1,323,972     |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | 0             | (82,515)      |
| 12 months or longer                                                                                                        | (381,142)     | (311,802)     |
| FHLMC and FNMA - Commercial                                                                                                |          |          |
| **Fair Value**                                                                                                             |          |          |
| Less than 12 months                                                                                                        | 0             | 51,299        |
| 12 months or longer                                                                                                        | 88,888        | 44,691        |
| **Unrealized Losses**                                                                                                      |          |          |
| Less than 12 months                                                                                                        | 0             | (3,099)       |
| 12 months or longer                                                                                                        | $ (2,933)     | $ (1,009)     |

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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.
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