Estimated Fair Value of Financial Instruments - Assets Measured by Fair Value on a Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified

Sep. 30, 2012

Dec. 31, 2011

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

$ 235,334

$ 226,012

Recurring [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

235,334

226,012

Recurring [Member] | U.S. Government agencies and corporations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

47,491

56,881

Recurring [Member] | Mortgage backed securities [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

129,987

107,037

Recurring [Member] | Collateralized mortgage obligations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

26,054

30,237

Recurring [Member] | State and political subdivisions [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

31,802

31,857

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring [Member] | U.S. Government agencies and corporations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring [Member] | Mortgage backed securities [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring [Member] | Collateralized mortgage obligations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring [Member] | State and political subdivisions [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Significant Other Observable Inputs (Level 2) [Member] | Recurring [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

235,334

226,012

Significant Other Observable Inputs (Level 2) [Member] | Recurring [Member] | U.S. Government agencies and corporations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

47,491

56,881

Significant Other Observable Inputs (Level 2) [Member] | Recurring [Member] | Mortgage backed securities [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

129,987

107,037

Significant Other Observable Inputs (Level 2) [Member] | Recurring [Member] | Collateralized mortgage obligations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

26,054

30,237

Significant Other Observable Inputs (Level 2) [Member] | Recurring [Member] | State and political subdivisions [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

31,802

31,857

Significant Unobservable Inputs (Level 3) [Member] | Recurring [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Significant Unobservable Inputs (Level 3) [Member] | Recurring [Member] | U.S. Government agencies and corporations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Significant Unobservable Inputs (Level 3) [Member] | Recurring [Member] | Mortgage backed securities [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Significant Unobservable Inputs (Level 3) [Member] | Recurring [Member] | Collateralized mortgage obligations [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

Significant Unobservable Inputs (Level 3) [Member] | Recurring [Member] | State and political subdivisions [Member]

Fair Value Of Other Financial Instrument [Line Items]

Securities available for sale, at fair value

- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (b)-(g)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-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 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-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 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-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.

+ Details