Annual report pursuant to Section 13 and 15(d)

PARTICIPATION IN THE SMALL BUSINESS LENDING FUND OF THE U.S. TREASURY DEPARTMENT - Additional Information (Detail)

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PARTICIPATION IN THE SMALL BUSINESS LENDING FUND OF THE U.S. TREASURY DEPARTMENT - Additional Information (Detail) (USD $)
 12 Months Ended
Jun. 21, 2011
Jun. 21, 2011
Senior Non Cumulative Perpetual Preferred Stock [Member]
Mar. 15, 2013
Series Preferred Stock [Member]
Dec. 31, 2012
Series Preferred Stock [Member]
Dec. 31, 2011
Series Preferred Stock [Member]
Dec. 31, 2010
Series Preferred Stock [Member]
Dec. 31, 2011
Qualified Small Business Lending [Member]
Dec. 31, 2011
Second Through Tenth Dividend Periods [Member]
Maximum [Member]
Dec. 31, 2011
Second Through Tenth Dividend Periods [Member]
Minimum [Member]
Dec. 31, 2011
Eleventh Through First Half Of Nineteenth Dividend [Member]
Maximum [Member]
Dec. 31, 2011
Eleventh Through First Half Of Nineteenth Dividend [Member]
Minimum [Member]
Dec. 31, 2011
More Than Four and One Half Years [Member]
Fixed Rate [Member]
Preferred stock, shares issued   40,000   40,000 40,000 0            
Preferred stock, liquidation preference   $ 1,000   $ 1,000 $ 1,000              
Preferred Stock, Liquidation Preference, Value   $ 40,000,000 $ 25,000,000                  
Fund Established Under Small Business Job Act 2010 30,000,000,000                      
Qualified Community Banks $ 10,000,000,000                      
Preferred Stock, Dividend Rate, Percentage             1.00% 5.00% 1.00% 7.00% 1.00% 9.00%