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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	$ 63	$ 124	$ 194	$ 95
Interest Rate Swap Contracts-Commercial Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	(21)	(11)	(8)	(19)
Interest Rate Lock Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	(8)	199	128	207
Forward Sale Contracts-Mortgage Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total Derivatives Gain (Loss)	$ 92	$ (64)	$ 74	$ (93)