Loans and Allowance - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended
Mar. 31, 2013 Loan	Mar. 31, 2013 Residential	Dec. 31, 2012 Residential	Mar. 31, 2013 Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate loans held for sale		$ 26,555	$ 22,300
Percentage of troubled debt restructured loans				50.00%
Number of troubled debt restructured loans	5

The aggregate carrying amount of loans receivable that will be sold to other entities. Includes mortgage and all other loans (collectively, loans) not classified as held for investment. Such loans are stated at the lower of cost or market, or elected fair value. Mortgage loans exclude mortgage-backed securities which are considered a debt security (other loan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

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+ Details