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INVESTMENT SECURITIES - Summary of Amortized Cost and Approximate Fair Value of Investment Securities (Detail) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2025 | Jun. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Jun. 30, 2024 | Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | $ 2,045,324 | $ 2,045,324 |  | $ 2,087,881 |  |  |
Allowance for Credit Losses | (24,064) | (24,064) | $ (17,356) | (7,604) | $ (4,639) | $ (5,339) | $ (3,952)
Gross Unrealized Gains | 9,915 | 9,915 |  | 732 |  |  |
Gross Unrealized Losses | (51,343) | (51,343) |  | (95,571) |  |  |
Fair Value | 1,979,832 | 1,979,832 |  | 1,985,438 |  |  |
Equity securities | 30,988 | 30,988 |  | 34,256 |  |  |
Total investment securities, at fair value | 2,010,820 | 2,010,820 |  | 2,019,694 |  |  |
Available-for-sale debt securities, accrued interest | 9,400 | 9,400 |  | 15,000 |  |  |
Impairment loss on securities without a readily determinable fair value | 0 | 2,300 |  |  |  |  |
Asset-backed securities |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 281,612 | 281,612 |  | 14,820 |  |  |
Allowance for Credit Losses | (196) | (196) | (584) | (362) | (307) | (367) | (483)
Gross Unrealized Gains | 800 | 800 |  | 0 |  |  |
Gross Unrealized Losses | (377) | (377) |  | (1,222) |  |  |
Fair Value | 281,839 | 281,839 |  | 13,236 |  |  |
Agency-guaranteed residential mortgage-backed securities |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 439,938 | 439,938 |  | 330,637 |  |  |
Allowance for Credit Losses | 0 | 0 |  | 0 |  |  |
Gross Unrealized Gains | 4,288 | 4,288 |  | 146 |  |  |
Gross Unrealized Losses | (140) | (140) |  | (3,745) |  |  |
Fair Value | 444,086 | 444,086 |  | 327,038 |  |  |
Agency-guaranteed residential collateralized mortgage obligations |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 488,233 | 488,233 |  | 242,858 |  |  |
Allowance for Credit Losses | 0 | 0 |  | 0 |  |  |
Gross Unrealized Gains | 2,987 | 2,987 |  | 0 |  |  |
Gross Unrealized Losses | (8,606) | (8,606) |  | (16,112) |  |  |
Fair Value | 482,614 | 482,614 |  | 226,746 |  |  |
Agency-guaranteed commercial collateralized mortgage obligations |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 96,660 | 96,660 |  | 95,850 |  |  |
Allowance for Credit Losses | 0 | 0 |  | 0 |  |  |
Gross Unrealized Gains | 540 | 540 |  | 44 |  |  |
Gross Unrealized Losses | (2,411) | (2,411) |  | (2,819) |  |  |
Fair Value | 94,789 | 94,789 |  | 93,075 |  |  |
Collateralized loan obligations |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 10,809 | 10,809 |  | 257,500 |  |  |
Allowance for Credit Losses | 0 | 0 |  | 0 |  |  |
Gross Unrealized Gains | 0 | 0 |  | 100 |  |  |
Gross Unrealized Losses | (149) | (149) |  | (2,193) |  |  |
Fair Value | 10,660 | 10,660 |  | 255,407 |  |  |
Commercial mortgage-backed securities |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost |  |  |  | 78,707 |  |  |
Allowance for Credit Losses |  |  |  | 0 |  |  |
Gross Unrealized Gains |  |  |  | 0 |  |  |
Gross Unrealized Losses |  |  |  | (999) |  |  |
Fair Value |  |  |  | 77,708 |  |  |
Corporate notes |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 344,683 | 344,683 |  | 564,524 |  |  |
Allowance for Credit Losses | (23,868) | (23,868) | $ (16,772) | (7,135) | $ (4,332) | $ (4,972) | $ (3,469)
Gross Unrealized Gains | 1,300 | 1,300 |  | 347 |  |  |
Gross Unrealized Losses | (22,683) | (22,683) |  | (41,406) |  |  |
Fair Value | 299,432 | 299,432 |  | 516,330 |  |  |
Private label collateralized mortgage obligations |  |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |  |
Amortized Cost | 383,389 | 383,389 |  | 502,985 |  |  |
Allowance for Credit Losses | 0 | 0 |  | (107) |  |  |
Gross Unrealized Gains | 0 | 0 |  | 95 |  |  |
Gross Unrealized Losses | (16,977) | (16,977) |  | (27,075) |  |  |
Fair Value | $ 366,412 | $ 366,412 |  | $ 475,898 |  |  |

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