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	Jun. 30, 2013	Dec. 31, 2012
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	$ 80,349	$ 108,031
Derivative Assets, Fair Value	772	1,547
Derivative Liabilities, Fair Value	64	54
Interest rate locks with customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	38,348	51,768
Forward loan sale commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Notional Amount	42,001	56,263
Other Liabilities [Member] | Interest rate locks with customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities, Fair Value	64
Other Liabilities [Member] | Forward loan sale commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Liabilities, Fair Value		54
Other Assets [Member] | Interest rate locks with customers [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value		1,547
Other Assets [Member] | Forward loan sale commitments [Member]
Derivative Notional Amount And Fair Value By Balance Sheet Not Designated As Hedging Instrument [Line Items]
Derivative Assets, Fair Value	$ 772