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INVESTMENT SECURITIES - Summary of Available-for-Sale Debt Securities by Stated Maturity (Detail) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
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Debt Securities, Available-for-sale [Line Items] |  |
Due in one year or less, amortized cost | $ 54,158 |
Due after one year through five years, amortized cost | 199,897 |
Due after five years through ten years, amortized cost | 81,878 |
Due after ten years, amortized cost | 8,750 |
Amortized Cost | 2,045,324 | $ 2,087,881
Due in one year or less, fair value | 44,830 |
Due after one year through five years, fair value | 174,971 |
Due after five years through ten years, fair value | 70,755 |
Due after ten years, fair value | 8,876 |
Fair Value | 1,979,832 | 1,985,438
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 281,612 |
Amortized Cost | 281,612 | 14,820
Debt securities, available-for-sale, without single maturity date, fair value | 281,839 |
Fair Value | 281,839 | 13,236
Agency-guaranteed residential mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 439,938 |
Amortized Cost | 439,938 | 330,637
Debt securities, available-for-sale, without single maturity date, fair value | 444,086 |
Fair Value | 444,086 | 327,038
Agency-guaranteed residential collateralized mortgage obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 488,233 |
Amortized Cost | 488,233 | 242,858
Debt securities, available-for-sale, without single maturity date, fair value | 482,614 |
Fair Value | 482,614 | 226,746
Agency-guaranteed commercial collateralized mortgage obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 96,660 |
Amortized Cost | 96,660 | 95,850
Debt securities, available-for-sale, without single maturity date, fair value | 94,789 |
Fair Value | 94,789 | 93,075
Collateralized loan obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 10,809 |
Amortized Cost | 10,809 | 257,500
Debt securities, available-for-sale, without single maturity date, fair value | 10,660 |
Fair Value | 10,660 | 255,407
Private label collateralized mortgage obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Debt securities, available-for-sale, without single maturity date, amortized cost | 383,389 |
Amortized Cost | 383,389 | 502,985
Debt securities, available-for-sale, without single maturity date, fair value | 366,412 |
Fair Value | $ 366,412 | $ 475,898

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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 + Details
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