Derivative Instruments and Hedging Activities - Notional Amounts and Fair Values of Derivatives Not Designated as Hedging Instruments (Detail) (Not Designated as Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	$ 54,121	$ 32,601
Derivative Assets, Fair Value	660	346
Derivative Liabilities, Fair Value	90	0
Interest Rate Locks with Customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	25,926	15,176
Interest Rate Locks with Customers [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value	660	321
Interest Rate Locks with Customers [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities, Fair Value	0	0
Forward Loan Sale Commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	28,195	17,425
Forward Loan Sale Commitments [Member] | Other Assets [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value	0	25
Forward Loan Sale Commitments [Member] | Other Liabilities [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities, Fair Value	$ 90	$ 0