Securities - Gross Unrealized Losses, Aggregated by Investment Category and Length of Time (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	$ (9,604)	$ (4,842)
Fair Value, Less Than Twelve Months	137,638	256,800
Gross Unrealized Losses, Twelve Months and Over	(38,211)	(2,221)
Fair Value, Twelve Months and Over	255,941	63,659
Gross Unrealized Losses, Total	(47,815)	(7,063)
Fair Value, Total	393,579	320,459
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(1,522)	(1,598)
Fair Value, Less Than Twelve Months	29,827	89,177
Gross Unrealized Losses, Twelve Months and Over	(8,535)
Fair Value, Twelve Months and Over	65,335
Gross Unrealized Losses, Total	(10,057)	(1,598)
Fair Value, Total	95,162	89,177
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(1,066)	(1,898)
Fair Value, Less Than Twelve Months	22,597	86,739
Gross Unrealized Losses, Twelve Months and Over	(15,819)	(1,584)
Fair Value, Twelve Months and Over	115,423	41,738
Gross Unrealized Losses, Total	(16,885)	(3,482)
Fair Value, Total	138,020	128,477
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(3,176)	(1,050)
Fair Value, Less Than Twelve Months	33,338	63,157
Gross Unrealized Losses, Twelve Months and Over	(10,802)	(412)
Fair Value, Twelve Months and Over	56,926	16,434
Gross Unrealized Losses, Total	(13,978)	(1,462)
Fair Value, Total	90,264	79,591
State and Local Governments [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Unrealized Losses, Less Than Twelve Months	(3,840)	(296)
Fair Value, Less Than Twelve Months	51,876	17,727
Gross Unrealized Losses, Twelve Months and Over	(3,055)	(225)
Fair Value, Twelve Months and Over	18,257	5,487
Gross Unrealized Losses, Total	(6,895)	(521)
Fair Value, Total	$ 70,133	$ 23,214

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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Amount of accumulated unrealized loss on 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 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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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 less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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