Recorded Investment in Loans for Each Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	$ 280,246	$ 284,941
Accrued interest receivable	1,010	1,093
Net deferred loan origination fees and costs	220	202
Recorded investment in loans	281,476	286,236
Individually evaluated for impairment	5,820	7,583
Collectively evaluated for impairment	275,656	278,653
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	281,476	286,236
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	105,344	108,097
Accrued interest receivable	405	444
Net deferred loan origination fees and costs	53	62
Recorded investment in loans	105,802	108,603
Individually evaluated for impairment	1,974	2,370
Collectively evaluated for impairment	103,828	106,233
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	105,802	108,603
Land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	9,395	9,607
Accrued interest receivable	40	48
Net deferred loan origination fees and costs	2	2
Recorded investment in loans	9,437	9,657
Individually evaluated for impairment	130	125
Collectively evaluated for impairment	9,307	9,532
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	9,437	9,657
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	11,777	11,746
Accrued interest receivable	49	29
Net deferred loan origination fees and costs	(11)	(12)
Recorded investment in loans	11,815	11,763
Individually evaluated for impairment	260	403
Collectively evaluated for impairment	11,555	11,360
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	11,815	11,763
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	69,400	68,731
Accrued interest receivable	190	188
Net deferred loan origination fees and costs	(22)	(17)
Recorded investment in loans	69,568	68,902
Individually evaluated for impairment	1,406	2,836
Collectively evaluated for impairment	68,162	66,066
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	69,568	68,902
Commercial Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	18,333	18,612
Accrued interest receivable	49	53
Net deferred loan origination fees and costs	(9)	(10)
Recorded investment in loans	18,373	18,655
Individually evaluated for impairment	1,776	1,776
Collectively evaluated for impairment	16,597	16,879
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	18,373	18,655
Home Equity and Second Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	35,202	36,962
Accrued interest receivable	129	147
Net deferred loan origination fees and costs	207	177
Recorded investment in loans	35,538	37,286
Individually evaluated for impairment	274	73
Collectively evaluated for impairment	35,264	37,213
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	35,538	37,286
Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	30,795	31,186
Accrued interest receivable	148	184
Net deferred loan origination fees and costs	0	0
Recorded investment in loans	30,943	31,370
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	30,943	31,370
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	$ 30,943	$ 31,370