Investment Securities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Held-to-maturity, Restricted	$ 119,200,000		$ 368,800,000
Debt Securities, Available-for-sale, Restricted	$ 377,600,000		626,700,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	231
Other Investments and Securities, at Cost	$ 6,200,000		1,200,000
Federal Home Loan Bank Stock	42,800,000		25,200,000
Amortized Cost	978,690,000		898,702,000
Debt Securities, Available-for-Sale	817,603,000		762,661,000
Sales
Gross Losses	103,000	$ 0
Gross Gains	$ 0	0
US Government-sponsored Enterprises Debt Securities [Member]
Percent of Unrealized Losses	96.00%
Amortized Cost	$ 1,000,000		1,000,000
Debt Securities, Available-for-Sale	$ 887,000		$ 882,000
Corporate Debt Securities [Member]
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	8		6
Amortized Cost	$ 33,752,000		$ 32,010,000
Debt Securities, Available-for-Sale	29,468,000		$ 29,204,000
Equity Securities [Member]
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount	$ 0	$ 0