Derivative Instruments and Hedging Activities - Gains (Losses) Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivatives not designated as hedging instrument [Member]
Amounts Related To Interest Rate Derivatives Designated As Hedges Of Fair Value [Line Items]
Interest income-interest and fees on loans	$ 97	$ 130
Interest expense-interest on time deposits	(140)	40
Derivatives designated as hedging instruments [Member]
Amounts Related To Interest Rate Derivatives Designated As Hedges Of Fair Value [Line Items]
Interest income-interest and fees on loans	(97)	(130)
Interest expense-interest on time deposits	$ 143	$ (32)