Fixed/Floating Rate Junior Subordinated Deferrable Interest Debentures - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012	Dec. 15, 2006	Jul. 21, 2006
Securities Financing Transaction [Line Items]
Floating/fixed rate capital securities, issued		$ 8,000,000	$ 4,000,000
Capital contribution		247,000	124,000
Principal amount of junior subordinated deferrable interest debentures, acquired		$ 8,247,000	$ 4,124,000
Interest rate over three-month LIBOR		1.74%	1.74%
Right exercised, description	The Corporation exercised its right on July 22, 2010 to defer the payment of interest on its outstanding subordinated debentures for an indefinite period (which can be no longer than 20 consecutive quarterly periods). Further, pursuant to a written agreement between the Corporation and the Federal Reserve, the Corporation cannot pay any dividends on its subordinated debentures without the prior written consent of the Federal Reserve Bank. This and any future deferred distributions will continue to accrue interest at a current rate of LIBOR+1.74% for the $4.0 million of trust preferred securities issued in July 2006 and at a current rate of LIBOR+1.74% for the $8.0 million of trust preferred securities issued in December 2006.