Impaired Loans by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 3,490	$ 2,703
Unpaid Principal Balance	4,243	3,136
Average Recorded Investment	2,949	1,808
Interest Income Recognized	9	0
Interest Recognized-Cash Method	9	39
Recorded Investment	4,093	4,698
Unpaid Principal Balance	4,396	5,189
Related Allowance	1,652	1,658
Average Recorded Investment	4,612	5,622
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	9
Recorded Investment	7,583	7,401
Unpaid Principal Balance	8,639	8,325
Related Allowance	1,652	1,658
Average Recorded Investment	7,561	7,430
Interest Income Recognized	9	0
Interest Recognized-Cash Method	9	48
Residential
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,427	1,149
Unpaid Principal Balance	1,760	1,507
Average Recorded Investment	1,248	978
Interest Income Recognized	6	0
Interest Recognized-Cash Method	4	29
Recorded Investment	943	1,132
Unpaid Principal Balance	1,020	1,233
Related Allowance	213	183
Average Recorded Investment	1,110	2,035
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	9
Recorded Investment	2,370	2,281
Unpaid Principal Balance	2,780	2,740
Related Allowance	213	183
Average Recorded Investment	2,358	3,013
Interest Income Recognized	6	0
Interest Recognized-Cash Method	4	38
Land
Financing Receivable, Impaired [Line Items]
Recorded Investment	125	5
Unpaid Principal Balance	126	6
Average Recorded Investment	43	5
Interest Income Recognized	0	0
Interest Recognized-Cash Method	2	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	125	5
Unpaid Principal Balance	126	6
Related Allowance	0	0
Average Recorded Investment	43	5
Interest Income Recognized	0	0
Interest Recognized-Cash Method	2	0
Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment	403	247
Unpaid Principal Balance	413	249
Average Recorded Investment	315	261
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	56
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	403	247
Unpaid Principal Balance	413	249
Related Allowance	0	0
Average Recorded Investment	315	317
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,535	1,215
Unpaid Principal Balance	1,944	1,280
Average Recorded Investment	1,292	514
Interest Income Recognized	0	0
Interest Recognized-Cash Method	1	9
Recorded Investment	1,301	1,638
Unpaid Principal Balance	1,394	1,933
Related Allowance	275	539
Average Recorded Investment	1,542	1,208
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	2,836	2,853
Unpaid Principal Balance	3,338	3,213
Related Allowance	275	539
Average Recorded Investment	2,834	1,722
Interest Income Recognized	0	0
Interest Recognized-Cash Method	1	9
Commercial Business
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	14
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	1,776	1,928
Unpaid Principal Balance	1,909	2,023
Related Allowance	1,098	936
Average Recorded Investment	1,857	2,036
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	1,776	1,928
Unpaid Principal Balance	1,909	2,023
Related Allowance	1,098	936
Average Recorded Investment	1,857	2,050
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Home Equity and Second Mortgage
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	87
Unpaid Principal Balance	0	94
Average Recorded Investment	51	32
Interest Income Recognized	2	0
Interest Recognized-Cash Method	2	1
Recorded Investment	73	0
Unpaid Principal Balance	73	0
Related Allowance	66	0
Average Recorded Investment	103	282
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	73	87
Unpaid Principal Balance	73	94
Related Allowance	66	0
Average Recorded Investment	154	314
Interest Income Recognized	2	0
Interest Recognized-Cash Method	2	1
Other Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Average Recorded Investment	0	4
Interest Income Recognized	1	0
Interest Recognized-Cash Method	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	5
Interest Income Recognized	0	0
Interest Recognized-Cash Method	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	9
Interest Income Recognized	1	0
Interest Recognized-Cash Method	$ 0	$ 0

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Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5258-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953550-111524

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