Federal Home Loan Bank Advances - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances, collateralized	$ 185.0	$ 205.8
Federal Home Loan Bank advances, general borrowing limit	100.0
Maximum
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal Home Loan Bank advances, additional borrowing amount	$ 8.8

Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 17

-IssueDate 2006-05-01

-Chapter 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

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-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 14

-Subparagraph f, h

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

- Definition

Amount of maximum advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References+ Details