Loans and Leases - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential loans pledged for potential borrowings at the Federal Home Loan Bank of New York	$ 273,300,000		$ 203,100,000
Carrying value of loans acquired	1,600,000
Interest income on the loans acquired	43,000
Non-accrual loans included of troubled debt restructurings	2,300,000		3,400,000
Interest accrued on impaired loans	1,700,000	2,100,000	2,800,000
Unfunded lending reserve	1,100,000		1,100,000
Mortgages held for sale	901,000
Leases held for sale	0		0
Other repossessed assets owned	44,000		77,000
Other real estate owned	2,100,000		452,000
Home Equity and Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Overdraft balances included in home equity and consumer loans	$ 381,000		$ 532,000