Note 3 - Loans and Allowance for Loan Losses (Detail) - Loans by Class Modified as Troubled Debt Restructurings (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Real Estate Mortgage Residential [Member] | TDR Identified Current Period [Member]
Number of Loans	1	3
Pre-Modification Outstanding Recorded Investment	$ 72	$ 1,348
Post-Modification Outstanding Recorded Investment	72	1,360
Real Estate Mortgage Residential [Member]
Post-Modification Outstanding Recorded Investment	634	3,897
Real Estate Mortgage Farmland And Other Commercial Enterprises [Member] | TDR Identified Current Period [Member]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	8,796
Post-Modification Outstanding Recorded Investment	8,717
Real Estate Mortgage Farmland And Other Commercial Enterprises [Member]
Post-Modification Outstanding Recorded Investment	16,940	9,021
Consumer Unsecured [Member] | TDR Identified Current Period [Member]
Number of Loans	1
Pre-Modification Outstanding Recorded Investment	38
Post-Modification Outstanding Recorded Investment	38
Consumer Unsecured [Member]
Post-Modification Outstanding Recorded Investment	39
Real Estate Construction And Land Development [Member] | TDR Identified Current Period [Member]
Number of Loans		1
Pre-Modification Outstanding Recorded Investment		159
Post-Modification Outstanding Recorded Investment		159
Real Estate Construction And Land Development [Member]
Post-Modification Outstanding Recorded Investment	8,736	6,207
TDR Identified Current Period [Member]
Number of Loans	3	4
Pre-Modification Outstanding Recorded Investment	8,906	1,507
Post-Modification Outstanding Recorded Investment	$ 8,827	$ 1,519