Investment Securities - Gross Unrealized Losses on Debt Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	$ 1,708,871	$ 1,393,098
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(92,589)	(14,640)
Debt Securities, Available for Sale, 12 Months or more, Fair Value	337,547	153,834
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss	(22,777)	(2,165)
Debt Securities, Available for Sale, Fair Value	2,046,418	1,546,932
Debt Securities, Available-for-sale, Unrealized Loss	(115,366)	(16,805)
Obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	1,385,647	947,108
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(79,940)	(9,737)
Debt Securities, Available for Sale, 12 Months or more, Fair Value	220,899	44,086
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss	(19,112)	(1,293)
Debt Securities, Available for Sale, Fair Value	1,606,546	991,194
Debt Securities, Available-for-sale, Unrealized Loss	(99,052)	(11,030)
Debt Securities Held to Maturity, Less than 12 months, Fair Value	147,078
Debt Securities, Held-to-maturity, Less than 12 Months, Unrealized	(3,070)
Debt Securities Held to Maturity, 12 months or more, Fair Value	0
Debt Securities, Held-to-maturity, 12 Months or Longer, Unrealized loss	0
Debt Securities, Held-to-maturity, Fair value	147,078
Debt Securities, Held-to-maturity, Unrealized loss	(3,070)
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	106,944	56,153
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(10,040)	(785)
Debt Securities, Available for Sale, 12 Months or more, Fair Value	9,045	0
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss	(1,364)	0
Debt Securities, Available for Sale, Fair Value	115,989	56,153
Debt Securities, Available-for-sale, Unrealized Loss	(11,404)	(785)
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	4,112
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(65)
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	4,112
Debt Securities, Available-for-sale, Unrealized Loss	(65)
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available for Sale, Less than 12 Months, Fair Value	212,168	389,837
Debt Securities, Available for Sale, Less than 12 Months, Unrealized Loss	(2,544)	(4,118)
Debt Securities, Available for Sale, 12 Months or more, Fair Value	107,603	109,748
Debt Securities, Available for Sale, 12 Months or more, Unrealized Loss	(2,301)	(872)
Debt Securities, Available for Sale, Fair Value	319,771	499,585
Debt Securities, Available-for-sale, Unrealized Loss	$ (4,845)	$ (4,990)

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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