Investment Securities - Narrative (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($) Investment	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) Investment	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Carrying value of securities pledged to secure public deposits and other contractual obligations	$ 456,600		$ 464,000
Pledging requirements for credit derivatives and SWAP agreements - securities		$ 0	$ 0
Number of investments in non federal issuer representing more than 10% of shareholder's equity | Investment	0		0
Maximum investment in any single non-federal issuer representing shareholders equity	10.00%		10.00%
Fair value HTM in unrealized loss with no ACL	$ 124,022		$ 128,277
Unrealized loss included in fair value of securities HTM in unrealized loss position for which an ACL has not been recorded	19,452		17,500
Fair value AFS in unrealized loss with no ACL	261,823		258,855
Unrealized loss included in fair value of securities AFS in unrealized loss position for which an ACL has not been recorded	39,398		35,629
Fair value of securities AFS in unrealized loss position for which an ACL has been recorded, net of allowance	77,800
Unrealized loss position included in fair value of securities AFS in unrealized loss position for which an ACL has been recorded	7,900
Allowance for credit losses	817		731
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair value AFS in unrealized loss with no ACL	5,494		780
Unrealized loss included in fair value of securities AFS in unrealized loss position for which an ACL has not been recorded	6		1
Allowance for credit losses	$ 817	1,432	$ 731	$ 1,140
Number of securities | Investment	36
Available-for-sale Securities
Debt Securities, Available-for-sale [Line Items]
Accrued interest receivable	$ 1,200
Allowance for credit losses	817
Other noninterest income | Equity Securities
Debt Securities, Available-for-sale [Line Items]
Net realized gain on investment securities	$ (36)	$ (69)