Investment Securities - Summary of Available-for-Sale Debt Securities by Stated Maturity (Detail) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, amortized cost	$ 0
Due after one years through five years, amortized cost	436,185
Due after five through ten years, amortized cost	151,666
Amortized Cost	3,242,361	$ 3,799,851
Due in one year or less, fair value	0
Due after one years through five years, fair value	411,856
Due after five through ten years, fair value	141,725
Total Debt Securities Fair Value	3,120,111	3,791,575
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	223,661
Amortized Cost	223,661	297,291
Debt securities, available-for-sale, without single maturity date, fair value	219,721
Total Debt Securities Fair Value	219,721	297,425
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	974,213
Amortized Cost	974,213	1,067,770
Debt securities, available-for-sale, without single maturity date, fair value	950,568
Total Debt Securities Fair Value	950,568	1,066,802
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	138,972
Amortized Cost	138,972	149,054
Debt securities, available-for-sale, without single maturity date, fair value	135,784
Total Debt Securities Fair Value	135,784	148,927
Agency-guaranteed residential collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	156,339
Amortized Cost	156,339	199,091
Debt securities, available-for-sale, without single maturity date, fair value	147,120
Total Debt Securities Fair Value	147,120	196,930
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, without single maturity date, amortized cost	1,161,325
Amortized Cost	1,161,325	1,248,142
Debt securities, available-for-sale, without single maturity date, fair value	1,113,337
Total Debt Securities Fair Value	$ 1,113,337	$ 1,242,465

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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