Investment Securities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Held-to-maturity, Restricted	$ 340,900,000		$ 313,900,000
Debt Securities, Available-for-sale, Restricted	$ 647,900,000		759,100,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	218
Other Investments and Securities, at Cost	$ 1,200,000		1,200,000
Federal Home Loan Bank Stock	14,300,000		11,700,000
Amortized Cost	926,875,000		1,045,579,000
Debt Securities, Available-for-Sale	$ 787,415,000		1,041,380,000
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	$ 873,000		$ 981,000
Corporate Debt Securities [Member]
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	6		6
Amortized Cost	$ 32,030,000		$ 32,088,000
Debt Securities, Available-for-Sale	29,315,000		$ 32,949,000
Equity Securities [Member]
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount	$ 0	$ 0