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Investment Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($) investmentSecurity securityLoan	Sep. 30, 2024 USD ($)	Sep. 30, 2025 USD ($) investmentSecurity securityLoan	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Investment Securities [Line Items]
Proceeds from the sale of investment securities	$ 28,500,000	$ 0	$ 58,500,000	$ 28,600,000
Gross realized losses from the sale of investment securities	2,100,000		3,300,000	$ 2,900,000
Securities pledged as collateral	853,600,000		853,600,000		$ 716,000,000.0
Residential real estate mortgage-backed securities	1,200,000,000		$ 1,200,000,000
Life of mortgage-backed securities			6 years
Allowance for credit loss	0		$ 0		$ 0
Obligations of U.S. government agencies
Investment Securities [Line Items]
Impairment losses recognized	0		0
Allowance for credit losses	$ 0		$ 0
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity	133		133
Percentage of aggregate depreciation in unrealized losses	11.25%		11.25%
Obligations of states and political subdivisions
Investment Securities [Line Items]
Impairment losses recognized	$ 0		$ 0
Allowance for credit losses	$ 0		$ 0
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity	147		147
Percentage of aggregate depreciation in unrealized losses	9.76%		9.76%
Corporate bonds
Investment Securities [Line Items]
Impairment losses recognized	$ 0		$ 0
Allowance for credit losses	$ 0		$ 0
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity	4		4
Percentage of aggregate depreciation in unrealized losses	2.05%		2.05%
Asset backed securities
Investment Securities [Line Items]
Impairment losses recognized	$ 0		$ 0
Allowance for credit losses	$ 0		$ 0
Number of available for sale securities in unrealized loss position (in investment securities) | investmentSecurity	18		18
Percentage of aggregate depreciation in unrealized losses	1.77%		1.77%
Non-agency collateralized mortgage obligations
Investment Securities [Line Items]
Allowance for credit losses	$ 0		$ 0
Number of available for sale securities in unrealized loss position (in investment securities) | securityLoan	14		14
Percentage of aggregate depreciation in unrealized losses	12.83%		12.83%

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Debt Securities, Credit Losses and Impairments Recognized in Earnings

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Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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