Derivative Instruments and Hedging Activities - Amount of Gain or Loss Recognized in Income on Derivatives (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	$ 94	$ (66)	$ 290	$ 30
Interest Rate Swap Contracts - Commercial Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	29	(10)	20	(29)
Interest Rate Lock Commitments - Mortgage Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	208	(105)	339	102
Forward Sale Contracts - Mortgage Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	$ (143)	$ 49	$ (69)	$ (43)