Loans, Leases and Other Real Estate - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017	Jul. 01, 2016	Jan. 07, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings included in non accrual loans	$ 3,800,000			$ 2,700,000
Unfunded lending reserve	2,500,000			2,500,000
Other real estate owned	1,400,000			843,000
Other repossessed assets owned	0			0
Residential Property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other real estate owned	1,100,000			843,000
Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on credit impaired loans	177,000		$ 151,000
Interest accrued on impaired loans	307,000		345,000
Pascack Bancorp, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and debt securities acquired with deteriorated credit quality	182,000
Total purchased credit impaired loans, experienced further credit deterioration and fully charged off			$ 127,000
Remaining loan amount paid		$ 218,000
Harmony Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and debt securities acquired with deteriorated credit quality	516,000
Certain loans acquired in transfer not accounted for as debt securities, carrying amount, decrease since acquisition					$ 253,000	$ 635,000
Remaining loan amount paid		$ 247,000
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	1,100,000,000			1,100,000,000
Home equity and consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdraft balances included in home equity and consumer loans	427,000			966,000
Residential Mortgages And Consumer Home Equity Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans that were in process of foreclosure	1,600,000			$ 2,700,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Group of impaired loans with recorded investment	$ 500,000