Recorded Investment in Loans for Each Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	$ 287,740	$ 284,941
Accrued interest receivable	1,014	1,093
Net deferred loan origination fees and costs	255	202
Recorded investment in loans	289,009	286,236
Individually evaluated for impairment	5,379	7,583
Collectively evaluated for impairment	283,630	278,653
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	289,009	286,236
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	107,773	108,097
Accrued interest receivable	418	444
Net deferred loan origination fees and costs	58	62
Recorded investment in loans	108,249	108,603
Individually evaluated for impairment	1,821	2,370
Collectively evaluated for impairment	106,428	106,233
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	108,249	108,603
Land
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	10,155	9,607
Accrued interest receivable	52	48
Net deferred loan origination fees and costs	3	2
Recorded investment in loans	10,210	9,657
Individually evaluated for impairment	127	125
Collectively evaluated for impairment	10,083	9,532
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	10,210	9,657
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	12,068	11,746
Accrued interest receivable	27	29
Net deferred loan origination fees and costs	(12)	(12)
Recorded investment in loans	12,083	11,763
Individually evaluated for impairment	203	403
Collectively evaluated for impairment	11,880	11,360
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	12,083	11,763
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	70,306	68,731
Accrued interest receivable	186	188
Net deferred loan origination fees and costs	(23)	(17)
Recorded investment in loans	70,469	68,902
Individually evaluated for impairment	1,127	2,836
Collectively evaluated for impairment	69,342	66,066
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	70,469	68,902
Commercial Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	21,395	18,612
Accrued interest receivable	54	53
Net deferred loan origination fees and costs	(9)	(10)
Recorded investment in loans	21,440	18,655
Individually evaluated for impairment	1,776	1,776
Collectively evaluated for impairment	19,664	16,879
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	21,440	18,655
Home Equity and Second Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	33,821	36,962
Accrued interest receivable	118	147
Net deferred loan origination fees and costs	238	177
Recorded investment in loans	34,177	37,286
Individually evaluated for impairment	325	73
Collectively evaluated for impairment	33,852	37,213
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	34,177	37,286
Other Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal loan balance	32,222	31,186
Accrued interest receivable	159	184
Net deferred loan origination fees and costs	0	0
Recorded investment in loans	32,381	31,370
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	32,381	31,370
Acquired with deteriorated credit quality	0	0
Recorded investment in loans	$ 32,381	$ 31,370