Investment Securities - Summary of Available-for-Sale Debt Securities by Stated Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, amortized cost	$ 7,500
Due after one year through five years, amortized cost	506,934
Due after five years through ten years, amortized cost	128,425
Amortized Cost	3,069,336	$ 3,138,534
Due in one year or less, fair value	7,500
Due after one year through five years, fair value	469,143
Due after five years through ten years, fair value	110,152
Fair Value	2,900,259	2,961,015
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	154,151
Amortized Cost	154,151	169,170
Debt securities, available-for-sale, without single maturity date, fair value	147,935
Fair Value	147,935	160,542
Agency-guaranteed residential collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	143,717
Amortized Cost	143,717	147,481
Debt securities, available-for-sale, without single maturity date, fair value	133,753
Fair Value	133,753	133,864
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	875,303
Amortized Cost	875,303	896,992
Debt securities, available-for-sale, without single maturity date, fair value	854,100
Fair Value	854,100	872,738
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	142,050
Amortized Cost	142,050	142,222
Debt securities, available-for-sale, without single maturity date, fair value	136,818
Fair Value	136,818	136,357
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	1,111,256
Amortized Cost	1,111,256	1,125,583
Debt securities, available-for-sale, without single maturity date, fair value	1,040,858
Fair Value	$ 1,040,858	$ 1,062,261

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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