Held to Maturity Debt Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Accrued interest on held to maturity debt securities	$ 3,100,000	$ 3,400,000
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Accrued interest receivable	Accrued interest receivable
Allowance for credit losses	$ 31,000	$ 27,000
Held to maturity securities at carrying value	317,600,000	340,200,000
Recognized gain on calls of securities held to maturity portfolio	45,000	123,000	$ 25,000
Recognized loss on calls of securities held to maturity portfolio	15,000	0	0
Proceeds from maturities, calls and paydowns of investment securities held to maturity	40,816,000	73,841,000	47,637,000
Sales of securities from held to maturity debt securities	$ 0	$ 0	0
Number of securities in an unrealized loss position | security	372	439
AAA
Schedule of Held-to-maturity Securities [Line Items]
Amount of total portfolio	17.00%
AA
Schedule of Held-to-maturity Securities [Line Items]
Amount of total portfolio	44.00%
A
Schedule of Held-to-maturity Securities [Line Items]
Amount of total portfolio	39.00%
Fitch, A Rating Or Not Rated
Schedule of Held-to-maturity Securities [Line Items]
Amount of total portfolio	1.00%
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Proceeds from maturities, calls and paydowns of investment securities held to maturity	$ 11,600,000	$ 39,200,000	$ 36,000,000