Note 4. Loans and Allowance for Loan Losses (Detail) - Aging of the Recorded Investment of Past Due Loans (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
30-59 Days Past Due	$ 4,800	$ 5,733
60-89 Days Past Due	2,234	1,738
90 or More Days Past Due	4,873	3,125
Total Past Due	11,907	10,596
Loans Not Past Due	552,167	587,712
Total	564,074	598,308
Residential Real Estate Loans [Member]
30-59 Days Past Due	1,981	3,731
60-89 Days Past Due	1,382	1,144
90 or More Days Past Due	2,681	2,975
Total Past Due	6,044	7,850
Loans Not Past Due	227,086	230,640
Total	233,130	238,490
Commercial Real Estate Owner Occupied [Member]
30-59 Days Past Due	1,717	182
90 or More Days Past Due	38	125
Total Past Due	1,755	307
Loans Not Past Due	108,516	131,996
Total	110,271	132,303
Commercial Real Estate Nonowner Occupied [Member]
60-89 Days Past Due	472	232
90 or More Days Past Due	487
Total Past Due	959	232
Loans Not Past Due	48,939	53,449
Total	49,898	53,681
Construction [Member]
30-59 Days Past Due		204
90 or More Days Past Due	1,574
Total Past Due	1,574	204
Loans Not Past Due	22,166	21,267
Total	23,740	21,471
Commercial and Industrial [Member]
30-59 Days Past Due	114	171
60-89 Days Past Due		14
Total Past Due	114	185
Loans Not Past Due	45,868	45,015
Total	45,982	45,200
Automobile Loans [Member]
30-59 Days Past Due	516	864
60-89 Days Past Due	278	110
90 or More Days Past Due	32	13
Total Past Due	826	987
Loans Not Past Due	41,458	44,715
Total	42,284	45,702
Home Equity Loans [Member]
30-59 Days Past Due	165	75
60-89 Days Past Due		76
90 or More Days Past Due	5	5
Total Past Due	170	156
Loans Not Past Due	18,994	20,351
Total	19,164	20,507
Other Consumer Loans [Member]
30-59 Days Past Due	307	506
60-89 Days Past Due	102	162
90 or More Days Past Due	56	7
Total Past Due	465	675
Loans Not Past Due	39,140	40,279
Total	$ 39,605	$ 40,954