Loans - Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2013 Contract	Dec. 31, 2012 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	6	7
Pre-Modification Outstanding Recorded Investment	$ 10,702	$ 10,851
Post-Modification Outstanding Recorded Investment	10,702	10,851
Related Allowance	1,103	1,297
Real estate, construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	2	3
Pre-Modification Outstanding Recorded Investment	892	1,095
Post-Modification Outstanding Recorded Investment	892	1,095
Related Allowance	276	340
Real estate, mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	3	3
Pre-Modification Outstanding Recorded Investment	9,120	9,054
Post-Modification Outstanding Recorded Investment	9,120	9,054
Related Allowance	827	957
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts	1	1
Pre-Modification Outstanding Recorded Investment	690	702
Post-Modification Outstanding Recorded Investment	690	702
Related Allowance

Amount of allowance for credit losses related to receivables which had been measured under a general allowance for credit losses methodology that are now identified as troubled debt restructurings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 65

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7484272&loc=SL7484277-172609

+ Details

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 33

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953676-111524

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- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

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