Note 8 - Loans and the Allowance for Loan Losses (Detail) - Commercial Credit Exposure: Credit Risk Profile by Creditworthiness Category (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Financing Receivable	$ 520,649,000	$ 621,021,000
Risk Rating 1-2 [Member] | Commercial Loans [Member]
Financing Receivable	3,312,000	4,509,000	14,869,000
Risk Rating 1-2 [Member] | Agricultural [Member]
Financing Receivable	8,659,000	25,979,000	20,023,000
Risk Rating 1-2 [Member] | Agricultural Real Estate [Member]
Financing Receivable	15,580,000	14,832,000	14,327,000
Risk Rating 1-2 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable	24,411,000	26,075,000	11,712,000
Risk Rating 1-2 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	161,000	376,000	407,000
Risk Rating 1-2 [Member] | Total Commercial Loans [Member]
Financing Receivable	52,123,000	71,771,000	61,338,000
Risk Rating 3 [Member] | Commercial Loans [Member]
Financing Receivable	23,140,000	30,037,000	53,622,000
Risk Rating 3 [Member] | Agricultural [Member]
Financing Receivable	12,307,000	27,348,000	31,303,000
Risk Rating 3 [Member] | Agricultural Real Estate [Member]
Financing Receivable	18,609,000	24,142,000	21,672,000
Risk Rating 3 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable	74,378,000	87,772,000	72,560,000
Risk Rating 3 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	3,070,000	8,348,000	8,941,000
Risk Rating 3 [Member] | Total Commercial Loans [Member]
Financing Receivable	131,504,000	177,647,000	188,098,000
Risk Rating 3 [Member]
Financing Receivable	3,000	3,000	3,000
Risk Rating 4 [Member] | Commercial Loans [Member]
Financing Receivable	16,144,000	18,892,000	31,031,000
Risk Rating 4 [Member] | Agricultural [Member]
Financing Receivable	1,401,000	7,096,000	9,324,000
Risk Rating 4 [Member] | Agricultural Real Estate [Member]
Financing Receivable	13,780,000	13,434,000	10,016,000
Risk Rating 4 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable	61,469,000	54,909,000	40,664,000
Risk Rating 4 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	946,000	1,744,000	1,965,000
Risk Rating 4 [Member] | Total Commercial Loans [Member]
Financing Receivable	93,740,000	96,075,000	93,000,000
Risk Rating 4 [Member]
Financing Receivable	4,000	4,000	4,000
Risk Rating 5 [Member] | Commercial Loans [Member]
Financing Receivable	2,151,000	1,970,000	10,526,000
Risk Rating 5 [Member] | Agricultural [Member]
Financing Receivable		381,000	1,170,000
Risk Rating 5 [Member] | Agricultural Real Estate [Member]
Financing Receivable	1,089,000	1,769,000	1,928,000
Risk Rating 5 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable	13,130,000	4,582,000	29,112,000
Risk Rating 5 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	5,310,000		3,270,000
Risk Rating 5 [Member] | Total Commercial Loans [Member]
Financing Receivable	21,680,000	8,702,000	46,006,000
Risk Rating 5 [Member]
Financing Receivable	5,000	5,000	5,000
Risk Rating 6 [Member] | Commercial Loans [Member]
Financing Receivable	6,167,000	7,201,000	19,584,000
Risk Rating 6 [Member] | Agricultural [Member]
Financing Receivable	25,000	447,000	2,534,000
Risk Rating 6 [Member] | Agricultural Real Estate [Member]
Financing Receivable	2,571,000	4,647,000	1,448,000
Risk Rating 6 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable	57,514,000	61,111,000	47,523,000
Risk Rating 6 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	18,776,000	35,673,000	60,543,000
Risk Rating 6 [Member] | Total Commercial Loans [Member]
Financing Receivable	85,053,000	109,079,000	131,632,000
Risk Rating 6 [Member]
Financing Receivable	6,000	6,000	6,000
Risk Rating 7 [Member] | Commercial Loans [Member]
Financing Receivable			139,000
Risk Rating 7 [Member] | Agricultural [Member]
Financing Receivable			0
Risk Rating 7 [Member] | Agricultural Real Estate [Member]
Financing Receivable	1,699,000	1,699,000	0
Risk Rating 7 [Member] | Commercial Real Estate Loans [Member]
Financing Receivable		654,000	0
Risk Rating 7 [Member] | Commercial Real Estate Development [Member]
Financing Receivable	1,861,000	12,138,000	0
Risk Rating 7 [Member] | Total Commercial Loans [Member]
Financing Receivable	3,560,000	14,491,000	139,000
Risk Rating 7 [Member]
Financing Receivable	7,000	7,000	7,000
Commercial Loans [Member]
Financing Receivable	50,914,000	62,609,000	129,771,000
Agricultural [Member]
Financing Receivable	22,392,000	61,251,000	64,354,000
Agricultural Real Estate [Member]
Financing Receivable	53,328,000	60,523,000	49,391,000
Commercial Real Estate Loans [Member]
Financing Receivable	230,902,000	235,103,000	201,571,000
Commercial Real Estate Development [Member]
Financing Receivable	30,124,000	58,279,000	75,126,000
Total Commercial Loans [Member]
Financing Receivable	$ 387,660,000	$ 477,765,000	$ 520,213,000