Investment Securities - Gross Unrealized Losses on Debt Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value		$ 274,950
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss		(4,845)
Debt Securities, Available for Sale, 12 Months or more, Fair Value		123,833
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss		(2,489)
Debt Securities, Available for Sale, Fair Value		398,783
Debt Securities, Available-for-sale, Unrealized Loss		(7,334)
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	$ 153,086	237,463
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(2,742)	(4,535)
Debt Securities, Available for Sale, 12 Months or more, Fair Value	291,893	99,981
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss	(13,791)	(2,378)
Debt Securities, Available for Sale, Fair Value	444,979	337,444
Debt Securities, Available-for-sale, Unrealized Loss	$ (16,533)	(6,913)
Obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value		36,709
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss		(309)
Debt Securities, Available for Sale, 12 Months or more, Fair Value		23,852
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss		(111)
Debt Securities, Available for Sale, Fair Value		60,561
Debt Securities, Available-for-sale, Unrealized Loss		(420)
Debt Securities Held to Maturity, Less than 12 months, Fair Value		18,813
Debt Securities Held to Maturity, Less than 12 months, Unrealized Loss		(142)
Debt Securities Held to Maturity, 12 months or more, Fair Value		62,952
Debt Securities Held to Maturity, 12 months or more, Unrealized Loss		(338)
Debt Securities Held to Maturity, Fair Value		81,765
Debt Securities Held to Maturity, Unrealized Loss		(480)
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value		778
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss		(1)
Debt Securities, Available for Sale, 12 Months or more, Fair Value		0
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss		0
Debt Securities, Available for Sale, Fair Value		778
Debt Securities, Available-for-sale, Unrealized Loss		$ (1)

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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