Financial Instruments with Off-Balance-Sheet Risk - Schedule of Financial Instruments with Off-Balance-Sheet Risk (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	$ 431,243
Unfunded lines of credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	335,654
Unfunded commitments to extend credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	75,604
Standby letters of credit [Member]
Concentration Risk [Line Items]
Financial instruments whose contract amounts represent credit risk	$ 19,985

Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13537-108611

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 15A

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration