Loans and Other Real Estate - Narrative (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings included in non accrual loans	$ 2,200,000		$ 1,600,000
Unfunded lending reserve	2,000,000.0		1,800,000
Other real estate owned	393,000		563,000
Other repossessed assets owned	0		0
Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on credit impaired loans	97,000	$ 144,000
Interest accrued on impaired loans	297,000	$ 268,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Group of impaired loans with recorded investment	500,000
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	1,500,000,000		1,300,000,000
Home equity and consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdraft balances included in home equity and consumer loans	281,000		789,000
Residential Mortgages and Consumer Home Equity Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans that were in process of foreclosure	$ 1,500,000		$ 2,000,000.0