Investment Securities - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Held-to-maturity, Restricted	$ 351,000,000		$ 313,900,000
Debt Securities, Available-for-sale, Restricted	$ 674,900,000		759,100,000
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	190
Other Investments and Securities, at Cost	$ 1,200,000		1,200,000
Federal Home Loan Bank Stock	12,500,000		11,700,000
Amortized Cost	956,870,000		1,045,579,000
Debt Securities, Available-for-Sale	$ 863,622,000		$ 1,041,380,000
US Government-sponsored Enterprises Debt Securities [Member]
Percent of Unrealized Losses	97.00%
Corporate Debt Securities [Member]
Investment Securities in Unrealized Loss Position, Qualitative Disclosure, Number of Positions, Total	4		4
Amortized Cost	$ 32,000,000		$ 32,100,000
Debt Securities, Available-for-Sale	31,000,000		$ 32,900,000
Equity Securities [Member]
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount	$ 0	$ 0