Borrowings - Additional Information (Detail) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Securities sold under agreements to repurchase	$ 29,400,000	$ 28,800,000
Advances from the FHLB	325,000,000	25,000,000
Securities Sold under Agreements to Repurchase
Debt Instrument [Line Items]
Pledged assets separately reported, mortgage-related securities available-for-sale or held-for-investment	20,900,000
Collateralized mortgage obligations, residential | Securities Sold under Agreements to Repurchase
Debt Instrument [Line Items]
Pledged assets separately reported, mortgage-related securities available-for-sale or held-for-investment	14,400,000
Line of Credit
Debt Instrument [Line Items]
Federal funds available for borrowing	175,600,000
Overnight federal funds borrowed	74,400,000	0
Line of Credit | Federal Reserve Bank of New York
Debt Instrument [Line Items]
Federal reserve bank, advances, amount of advances by branch	0	0
Federal Home Loan Bank of New York | Line of Credit
Debt Instrument [Line Items]
Overnight borrowings	$ 625,000,000	$ 700,000,000
Collateralized FHLB Advances | Weighted Average
Debt Instrument [Line Items]
Federal Home Loan Bank, advances, branch of FHLB Bank, interest rate	4.71%	0.77%