Estimated Fair Value of Financial Instruments - Assets Measured by Fair Value on a Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	$ 203,763	$ 226,012
U.S. Government agencies and corporations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	36,970	56,881
Mortgage backed securities
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	111,701	107,037
Collateralized mortgage obligations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	22,881	30,237
State and political subdivisions
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	32,211	31,857
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| U.S. Government agencies and corporations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Mortgage backed securities
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Collateralized mortgage obligations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| State and political subdivisions
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	203,763	226,012
Significant Other Observable Inputs (Level 2) [Member] \| U.S. Government agencies and corporations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	36,970	56,881
Significant Other Observable Inputs (Level 2) [Member] \| Mortgage backed securities
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	111,701	107,037
Significant Other Observable Inputs (Level 2) [Member] \| Collateralized mortgage obligations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	22,881	30,237
Significant Other Observable Inputs (Level 2) [Member] \| State and political subdivisions
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	32,211	31,857
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| U.S. Government agencies and corporations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Mortgage backed securities
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| Collateralized mortgage obligations
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	0	0
Significant Unobservable Inputs (Level 3) [Member] \| State and political subdivisions
Fair Value Of Other Financial Instrument [Line Items]
Securities available for sale, at fair value	$ 0	$ 0

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

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)

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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

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-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