Unearned ESOP Shares - Analysis of ESOP Shares Held in Suspense and Its Fair Value (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Employee Stock Ownership Plan (ESOP), Shares in ESOP [Rollforward]
Shares in suspense, beginning of the year	104,661	237,106
Shares allocated	(104,661)	(132,445)
Shares acquired	0	0
Shares in suspense, end of the year	0	104,661
Fair market value of shares in suspense	$ 0	$ 550

Shares contributed to the ESOP that have not yet been released, committed to be released, or allocated to participant accounts. Suspense shares generally collateralize ESOP debt.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 53

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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:sharesItemType
Balance Type:	na
Period Type:	instant