Loans and Other Real Estate - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings included in non accrual loans	$ 1,600,000	$ 3,600,000
Unfunded lending reserve	1,800,000	2,300,000
Loans to related parties	55,400,000	53,100,000
Loans to related parties, additions	21,400,000
Repayment of loan from related parties	19,100,000
Mortgages held for sale	1,743,000	1,113,000
Residential real estate acquired through disclosure	563,000	830,000
Other repossessed assets owned	0	0
Writedown of other repossessed assets	153,000	70,000	$ 98,000
Federal Home Loan Bank of New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential loans pledged for potential borrowings at the Federal Home Loan Bank of New York	1,300,000,000	1,200,000,000
Residential Property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate acquired through disclosure		702,000
Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest accrued on impaired loans and leases	1,000,000.0	1,100,000	$ 1,500,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Group of impaired loans with recorded investment	500,000
Home equity and consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdraft balances included in home equity and consumer loans	789,000	452,000
Residential Mortgages and Consumer Home Equity Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans that were in process of foreclosure	$ 2,000,000.0	$ 1,500,000