Loans and Allowance - Additional Information (Detail) (USD $)			3 Months Ended	9 Months Ended
Sep. 30, 2012	Feb. 10, 2012	Sep. 30, 2012 Residential Loan	Sep. 30, 2012 Residential Loan	Dec. 31, 2011 Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate loans held for sale			$ 27,711,000	$ 27,711,000	$ 17,864,000
Loan Acquired during acquisition	113,000,000	113,000,000
Fair Value Discount	$ 19,200,000
Percentage of troubled debt restructured loans			29.00%	48.00%
Number of troubled debt restructured loans			3	11

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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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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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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-Name Statement of Financial Accounting Standard (FAS)

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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