Commitments and Contingencies - Gains (Losses) Related to Interest Rate Derivatives Designated as Hedges of Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivatives not designated as hedging instrument [Member]
Interest income-interest and fees on loans	$ (57)	$ (761)	$ (361)
Interest expense-interest on time deposits	(200)	852
Derivatives designated as hedging Instruments [Member]
Interest income-interest and fees on loans	57	761	361
Interest expense-interest on time deposits	$ 220	$ (884)