INVESTMENT SECURITIES - Summary of Available-for-Sale Debt Securities by Stated Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Amortized Cost
Due in one year or less, amortized cost	$ 48,687
Due after one year through five years, amortized cost	108,891
Due after five years through ten years, amortized cost	114,628
Due after ten years, amortized cost	8,000
Amortized Cost	2,666,709	$ 1,982,147
Fair Value
Due in one year or less, fair value	38,561
Due after one year through five years, fair value	88,676
Due after five years through ten years, fair value	101,642
Due after ten years, fair value	8,000
Fair Value	2,595,966	1,906,535
Asset-backed securities
Amortized Cost
Debt securities, available-for-sale, without single maturity date, amortized cost	300,305
Amortized Cost	300,305	239,259
Fair Value
Debt securities, available-for-sale, without single maturity date, fair value	301,492
Fair Value	301,492	237,813
Agency-guaranteed residential mortgage-backed securities
Amortized Cost
Debt securities, available-for-sale, without single maturity date, amortized cost	754,024
Amortized Cost	754,024	410,648
Fair Value
Debt securities, available-for-sale, without single maturity date, fair value	750,995
Fair Value	750,995	413,761
Agency-guaranteed residential collateralized mortgage obligations
Amortized Cost
Debt securities, available-for-sale, without single maturity date, amortized cost	852,422
Amortized Cost	852,422	496,595
Fair Value
Debt securities, available-for-sale, without single maturity date, fair value	844,866
Fair Value	844,866	493,507
Agency-guaranteed commercial collateralized mortgage obligations
Amortized Cost
Debt securities, available-for-sale, without single maturity date, amortized cost	116,879
Amortized Cost	116,879	118,049
Fair Value
Debt securities, available-for-sale, without single maturity date, fair value	112,025
Fair Value	112,025	115,576
Private label collateralized mortgage obligations
Amortized Cost
Debt securities, available-for-sale, without single maturity date, amortized cost	362,873
Amortized Cost	362,873	376,803
Fair Value
Debt securities, available-for-sale, without single maturity date, fair value	349,709
Fair Value	$ 349,709	$ 360,020

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).

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