Note 4. Loans and Allowance for Loan Losses (Detail) - Allowance for Loan Losses Activity (USD $) In Thousands, unless otherwise specified			3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Residential Portfolio Segment [Member]	Jun. 30, 2011 Residential Portfolio Segment [Member]	Jun. 30, 2012 Residential Portfolio Segment [Member]	Jun. 30, 2011 Residential Portfolio Segment [Member]	Jun. 30, 2012 Residential Portfolio Segment [Member]	Dec. 31, 2011 Residential Portfolio Segment [Member]	Jun. 30, 2012 Commercial Real Estate Portfolio Segment [Member]	Jun. 30, 2011 Commercial Real Estate Portfolio Segment [Member]	Jun. 30, 2012 Commercial Real Estate Portfolio Segment [Member]	Jun. 30, 2011 Commercial Real Estate Portfolio Segment [Member]	Jun. 30, 2012 Commercial Real Estate Portfolio Segment [Member]	Dec. 31, 2011 Commercial Real Estate Portfolio Segment [Member]	Jun. 30, 2012 Commercial and Industrial [Member]	Jun. 30, 2011 Commercial and Industrial [Member]	Jun. 30, 2012 Commercial and Industrial [Member]	Jun. 30, 2011 Commercial and Industrial [Member]	Jun. 30, 2012 Commercial and Industrial [Member]	Dec. 31, 2011 Commercial and Industrial [Member]	Jun. 30, 2012 Consumer Portfolio Segment [Member]	Jun. 30, 2011 Consumer Portfolio Segment [Member]	Jun. 30, 2012 Consumer Portfolio Segment [Member]	Jun. 30, 2011 Consumer Portfolio Segment [Member]	Jun. 30, 2012 Consumer Portfolio Segment [Member]	Dec. 31, 2011 Consumer Portfolio Segment [Member]	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Allowance for loan losses:
Beginning balance	$ 7,527	$ 7,344	$ 1,491	$ 1,337	$ 1,730	$ 1,051	$ 1,443	$ 1,860	$ 3,423	$ 4,251	$ 3,623	$ 3,083	$ 4,369	$ 3,493	$ 623	$ 1,140	$ 636	$ 3,795	$ 653	$ 636	$ 1,310	$ 1,324	$ 1,355	$ 1,457	$ 1,062	$ 1,355	$ 6,847	$ 8,052	$ 7,344	$ 9,386
Provision for loan losses			18	489	295	1,014			1,004	(116)	1,896	985			(319)	421	(407)	1,605			(179)	(35)	56	99			524	759	1,840	3,703
Loans charged off			(85)	(722)	(678)	(969)			(62)	(1,547)	(1,158)	(1,587)				(862)	(70)	(4,701)			(298)	(330)	(817)	(747)			(445)	(3,461)	(2,723)	(8,004)
Recoveries			19	29	96	37			4	804	8	911			349	71	494	71			229	225	468	375			601	1,129	1,066	1,394
Total ending allowance balance	$ 7,527	$ 7,344	$ 1,443	$ 1,133	$ 1,443	$ 1,133	$ 1,443	$ 1,860	$ 4,369	$ 3,392	$ 4,369	$ 3,392	$ 4,369	$ 3,493	$ 653	$ 770	$ 653	$ 770	$ 653	$ 636	$ 1,062	$ 1,184	$ 1,062	$ 1,184	$ 1,062	$ 1,355	$ 7,527	$ 6,479	$ 7,527	$ 6,479