Loans, Leases and Other Real Estate - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Mar. 31, 2017	Jul. 01, 2016	Jan. 07, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings included in non accrual loans		$ 4,900,000		$ 2,700,000
Unfunded lending reserve		2,500,000		2,500,000
Other real estate owned		2,200,000		843,000
Other repossessed assets owned		0		0
Residential Property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other real estate owned		1,900,000		843,000
Impaired Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on credit impaired loans		308,000	$ 336,000
Interest accrued on impaired loans		566,000	$ 813,000
Pascack Bancorp, Inc.
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and debt securities acquired with deteriorated credit quality		175,000
Certain loans acquired in transfer not accounted for as debt securities, carrying amount, decrease since acquisition							$ 642,000
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		511,000
Certain loans acquired in transfer not accounted for as debt securities, carrying amount, decrease since acquisition						$ 258,000
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		1,200,000,000		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		356,000		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		2,300,000		$ 2,700,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Group of impaired loans with recorded investment		$ 500,000