Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 1,910		$ 1,910		$ 3,490
Unpaid Principal Balance	2,207		2,207		4,243
Average Recorded Investment	1,988	2,838	2,487	2,792
Interest Income Recognized	7	1	11	3
Interest Recognized-Cash Method	4	1	5	2
Recorded Investment	3,469		3,469		4,093
Unpaid Principal Balance	3,828		3,828		4,396
Related Allowance	1,347		1,347		1,652
Average Recorded Investment	3,614	4,575	3,774	4,615
Interest Income Recognized	0	0	1	0
Interest Recognized-Cash Method	0	1	0	1
Recorded Investment	5,379		5,379		7,583
Unpaid Principal Balance	6,035		6,035		8,639
Related Allowance	1,347		1,347		1,652
Average Recorded Investment	5,602	7,413	6,261	7,407
Interest Income Recognized	7	1	12	3
Interest Recognized-Cash Method	4	2	5	3
Residential
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,181		1,181		1,427
Unpaid Principal Balance	1,453		1,453		1,760
Average Recorded Investment	1,273	1,202	1,324	1,184
Interest Income Recognized	2	0	5	1
Interest Recognized-Cash Method	0	1	1	1
Recorded Investment	640		640		943
Unpaid Principal Balance	790		790		1,020
Related Allowance	93		93		213
Average Recorded Investment	625	1,017	731	1,055
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	1,821		1,821		2,370
Unpaid Principal Balance	2,243		2,243		2,780
Related Allowance	93		93		213
Average Recorded Investment	1,898	2,219	2,055	2,239
Interest Income Recognized	2	0	5	1
Interest Recognized-Cash Method	0	1	1	1
Land
Financing Receivable, Impaired [Line Items]
Recorded Investment	127		127		125
Unpaid Principal Balance	134		134		126
Average Recorded Investment	126	41	125	29
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment	3	0	2	0
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	127		127		125
Unpaid Principal Balance	134		134		126
Related Allowance	0		0		0
Average Recorded Investment	129	41	127	29
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Construction
Financing Receivable, Impaired [Line Items]
Recorded Investment	203		203		403
Unpaid Principal Balance	217		217		413
Average Recorded Investment	232	266	289	259
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	203		203		403
Unpaid Principal Balance	217		217		413
Related Allowance	0		0		0
Average Recorded Investment	232	266	289	259
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Commercial Real Estate
Financing Receivable, Impaired [Line Items]
Recorded Investment	139		139		1,535
Unpaid Principal Balance	141		141		1,944
Average Recorded Investment	106	1,244	582	1,234
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	988		988		1,301
Unpaid Principal Balance	1,063		1,063		1,394
Related Allowance	164		164		275
Average Recorded Investment	1,161	1,502	1,208	1,547
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	1,127		1,127		2,836
Unpaid Principal Balance	1,204		1,204		3,338
Related Allowance	164		164		275
Average Recorded Investment	1,267	2,746	1,790	2,781
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Commercial Business
Financing Receivable, Impaired [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	4	0	4	0
Interest Recognized-Cash Method	3	0	3	0
Recorded Investment	1,776		1,776		1,776
Unpaid Principal Balance	1,909		1,909		1,909
Related Allowance	1,065		1,065		1,098
Average Recorded Investment	1,776	1,885	1,776	1,899
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	1,776		1,776		1,776
Unpaid Principal Balance	1,909		1,909		1,909
Related Allowance	1,065		1,065		1,098
Average Recorded Investment	1,776	1,885	1,776	1,899
Interest Income Recognized	4	0	4	0
Interest Recognized-Cash Method	3	0	3	0
Home Equity and Second Mortgage
Financing Receivable, Impaired [Line Items]
Recorded Investment	260		260		0
Unpaid Principal Balance	262		262		0
Average Recorded Investment	251	85	167	86
Interest Income Recognized	1	1	2	2
Interest Recognized-Cash Method	1	0	1	1
Recorded Investment	65		65		73
Unpaid Principal Balance	66		66		73
Related Allowance	25		25		66
Average Recorded Investment	49	171	57	114
Interest Income Recognized	0	0	1	0
Interest Recognized-Cash Method	0	1	0	1
Recorded Investment	325		325		73
Unpaid Principal Balance	328		328		73
Related Allowance	25		25		66
Average Recorded Investment	300	256	224	200
Interest Income Recognized	1	1	3	2
Interest Recognized-Cash Method	1	1	1	2
Other Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	0	0	0	0
Recorded Investment	0		0		0
Unpaid Principal Balance	0		0		0
Related Allowance	0		0		0
Average Recorded Investment	0	0	0	0
Interest Income Recognized	0	0	0	0
Interest Recognized-Cash Method	$ 0	$ 0	$ 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=28368275&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=28368275&loc=d3e5258-111524

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-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

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