Derivative and Hedging Activities - Effect of Corporation's Derivative Financial Instruments on Income Statement (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Interest Rate Contracts [Member] | Interest Income - Loans and Leases [Member]
Derivative [Line Items]
Derivative financial instrument, net	$ 2,440	$ 2,479
Interest Rate Contracts [Member] | Interest Expense - Short-term Borrowings [Member]
Derivative [Line Items]
Derivative financial instrument, net	115
Interest Rate Swap [Member] | Other Income [Member]
Derivative [Line Items]
Derivative financial instrument, net	(364)	$ (9)
Credit Risk Contract [Member] | Other Income [Member]
Derivative [Line Items]
Derivative financial instrument, net	$ (170)