Note 4 - Loans and Allowance for Loan Losses (Detail) - Troubled Debt Restructurings (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Consumer:
Number of TDR loans	30	37
Balance on TDR loans (in Dollars)	$ 13,684	$ 16,542
Accruing TDR Loans [Member] | Other Consumer [Member]
Consumer:
Number of TDR loans	3	5
Balance on TDR loans (in Dollars)	46	23
Accruing TDR Loans [Member] | Consumer Loans [Member]
Consumer:
Number of TDR loans	3	5
Balance on TDR loans (in Dollars)	46	23
Accruing TDR Loans [Member] | Construction Loans [Member]
Consumer:
Number of TDR loans	2	1
Balance on TDR loans (in Dollars)	1,212	1,277
Accruing TDR Loans [Member] | Single Family Residential Loans [Member]
Consumer:
Number of TDR loans	3	5
Balance on TDR loans (in Dollars)	574	957
Accruing TDR Loans [Member] | Other Commercial Real Estate Loans [Member]
Consumer:
Number of TDR loans	15	13
Balance on TDR loans (in Dollars)	9,085	8,601
Accruing TDR Loans [Member] | Real Estate Loans [Member]
Consumer:
Number of TDR loans	20	19
Balance on TDR loans (in Dollars)	10,871	10,835
Accruing TDR Loans [Member] | Other Commercial Loans [Member]
Consumer:
Number of TDR loans	2	2
Balance on TDR loans (in Dollars)	78	332
Accruing TDR Loans [Member] | Commercial Loans [Member]
Consumer:
Number of TDR loans	2	4
Balance on TDR loans (in Dollars)	78	533
Accruing TDR Loans [Member] | Agricultural Loans [Member]
Consumer:
Number of TDR loans		2
Balance on TDR loans (in Dollars)		201
Accruing TDR Loans [Member]
Consumer:
Number of TDR loans	25	28
Balance on TDR loans (in Dollars)	10,995	11,391
Nonaccrual TDR Loans [Member] | Other Consumer [Member]
Consumer:
Number of TDR loans	0
Balance on TDR loans (in Dollars)	0
Nonaccrual TDR Loans [Member] | Consumer Loans [Member]
Consumer:
Number of TDR loans	0
Balance on TDR loans (in Dollars)	0
Nonaccrual TDR Loans [Member] | Construction Loans [Member]
Consumer:
Number of TDR loans	0
Balance on TDR loans (in Dollars)	0
Nonaccrual TDR Loans [Member] | Single Family Residential Loans [Member]
Consumer:
Number of TDR loans	1	1
Balance on TDR loans (in Dollars)	18	34
Nonaccrual TDR Loans [Member] | Other Commercial Real Estate Loans [Member]
Consumer:
Number of TDR loans	2	7
Balance on TDR loans (in Dollars)	2,347	5,082
Nonaccrual TDR Loans [Member] | Real Estate Loans [Member]
Consumer:
Number of TDR loans	3	8
Balance on TDR loans (in Dollars)	2,365	5,116
Nonaccrual TDR Loans [Member] | Other Commercial Loans [Member]
Consumer:
Number of TDR loans	2	1
Balance on TDR loans (in Dollars)	324	35
Nonaccrual TDR Loans [Member] | Commercial Loans [Member]
Consumer:
Number of TDR loans	2	1
Balance on TDR loans (in Dollars)	324	35
Nonaccrual TDR Loans [Member] | Agricultural Loans [Member]
Consumer:
Number of TDR loans		0
Balance on TDR loans (in Dollars)		0
Nonaccrual TDR Loans [Member]
Consumer:
Number of TDR loans	5	9
Balance on TDR loans (in Dollars)	2,689	5,151
Other Consumer [Member]
Consumer:
Number of TDR loans	3	5
Balance on TDR loans (in Dollars)	46	23
Consumer Loans [Member]
Consumer:
Number of TDR loans	3	5
Balance on TDR loans (in Dollars)	46	23
Construction Loans [Member]
Consumer:
Number of TDR loans	2	1
Balance on TDR loans (in Dollars)	1,212	1,277
Single Family Residential Loans [Member]
Consumer:
Number of TDR loans	4	6
Balance on TDR loans (in Dollars)	592	991
Other Commercial Real Estate Loans [Member]
Consumer:
Number of TDR loans	17	20
Balance on TDR loans (in Dollars)	11,432	13,683
Real Estate Loans [Member]
Consumer:
Number of TDR loans	23	27
Balance on TDR loans (in Dollars)	13,236	15,951
Other Commercial Loans [Member]
Consumer:
Number of TDR loans	4	3
Balance on TDR loans (in Dollars)	402	367
Commercial Loans [Member]
Consumer:
Number of TDR loans	4	5
Balance on TDR loans (in Dollars)	402	568
Agricultural Loans [Member]
Consumer:
Number of TDR loans		2
Balance on TDR loans (in Dollars)		$ 201