Investment Securities - Gross Unrealized Losses and Fair Value, Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	$ 3,055,315	$ 2,024,753
Less than 12 Months, Unrealized Losses	(73,883)	(15,567)
12 Months or More, Fair Value	156,695	6,818
12 Months or More, Unrealized Losses	(12,630)	(136)
Fair Value, Total	3,212,010	2,031,571
Unrealized Losses	(86,513)	(15,703)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	199,725	54,753
Less than 12 Months, Unrealized Losses	(3,832)	(119)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Fair Value, Total	199,725	54,753
Unrealized Losses	(3,832)	(119)
Agency-guaranteed residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	0	9,554
Less than 12 Months, Unrealized Losses	0	(312)
12 Months or More, Fair Value	8,269	0
12 Months or More, Unrealized Losses	(973)	0
Fair Value, Total	8,269	9,554
Unrealized Losses	(973)	(312)
Agency-guaranteed commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	2,045	2,152
Less than 12 Months, Unrealized Losses	(95)	(10)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Fair Value, Total	2,045	2,152
Unrealized Losses	(95)	(10)
Agency-guaranteed residential collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	434,524	173,492
Less than 12 Months, Unrealized Losses	(16,428)	(2,315)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Fair Value, Total	434,524	173,492
Unrealized Losses	(16,428)	(2,315)
Agency-guaranteed commercial collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	95,995	118,334
Less than 12 Months, Unrealized Losses	(3,764)	(3,877)
12 Months or More, Fair Value	66,605	0
12 Months or More, Unrealized Losses	(6,047)	0
Fair Value, Total	162,600	118,334
Unrealized Losses	(9,811)	(3,877)
Collateralized loan obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	934,954	715,250
Less than 12 Months, Unrealized Losses	(6,457)	(1,215)
12 Months or More, Fair Value	25,510	0
12 Months or More, Unrealized Losses	(119)	0
Fair Value, Total	960,464	715,250
Unrealized Losses	(6,576)	(1,215)
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	129,365	122,597
Less than 12 Months, Unrealized Losses	(1,368)	(180)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Fair Value, Total	129,365	122,597
Unrealized Losses	(1,368)	(180)
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	393,997	188,100
Less than 12 Months, Unrealized Losses	(13,972)	(1,561)
12 Months or More, Fair Value	14,115	0
12 Months or More, Unrealized Losses	(884)	0
Fair Value, Total	408,112	188,100
Unrealized Losses	(14,856)	(1,561)
Private label collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	856,760	632,091
Less than 12 Months, Unrealized Losses	(27,386)	(5,874)
12 Months or More, Fair Value	42,196	6,818
12 Months or More, Unrealized Losses	(4,607)	(136)
Fair Value, Total	898,956	638,909
Unrealized Losses	(31,993)	(6,010)
State and political subdivision debt securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Months, Fair Value	7,950	8,430
Less than 12 Months, Unrealized Losses	(581)	(104)
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Fair Value, Total	7,950	8,430
Unrealized Losses	$ (581)	$ (104)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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