Derivative Instruments and Hedging Activities - Amount of Gain or Loss Recognized in Income on Derivatives (Detail) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain	$ 116	$ 94	$ 419	$ 290
Interest Rate Swap Contracts - Commercial Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain	(87)	29	34	20
Interest Rate Lock Commitments - Mortgage Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain	97	208	478	339
Forward Sale Contracts - Mortgage Loans
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain	$ 106	$ (143)	$ (93)	$ (69)