Note 4 - Loans and Allowance for Loan Losses (Detail) - Impaired Loans, net of government guarantess and excluding loans acquired, segregated by class of loans: (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Total Recorded Investment	$ 30,800,000	$ 40,100,000
Related Allowance	2,800,000	3,500,000
Average Investment in Impaired Loans	34,800,000	46,700,000	55,800,000
Interest Income Recognized	1,800,000	2,100,000	2,400,000
Consumer Loans [Member] | Credit Cards [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	547,000	605,000
Recorded Investment With No Allowance	547,000	605,000
Total Recorded Investment	547,000	605,000
Related Allowance	82,000	91,000
Average Investment in Impaired Loans	565,000	715,000
Interest Income Recognized	16,000	44,000
Consumer Loans [Member] | Other Consumer [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	1,140,000	1,359,000
Recorded Investment With No Allowance	999,000	1,203,000
Recorded Investment With Allowance	131,000	128,000
Total Recorded Investment	1,130,000	1,331,000
Related Allowance	249,000	266,000
Average Investment in Impaired Loans	1,179,000	1,298,000
Interest Income Recognized	63,000	57,000
Consumer Loans [Member] | Total Consumer [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	1,687,000	1,964,000
Recorded Investment With No Allowance	1,546,000	1,808,000
Recorded Investment With Allowance	131,000	128,000
Total Recorded Investment	1,677,000	1,936,000
Related Allowance	331,000	357,000
Average Investment in Impaired Loans	1,744,000	2,013,000
Interest Income Recognized	79,000	101,000
Real Estate Loans [Member] | Construction Loans [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	5,443,000	5,324,000
Recorded Investment With No Allowance	3,866,000	3,783,000
Recorded Investment With Allowance	1,494,000	1,498,000
Total Recorded Investment	5,360,000	5,281,000
Related Allowance	505,000	415,000
Average Investment in Impaired Loans	5,466,000	6,758,000
Interest Income Recognized	291,000	298,000
Real Estate Loans [Member] | Single Family Residential Loans [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	4,091,000	5,152,000
Recorded Investment With No Allowance	2,877,000	4,243,000
Recorded Investment With Allowance	1,140,000	589,000
Total Recorded Investment	4,017,000	4,832,000
Related Allowance	494,000	402,000
Average Investment in Impaired Loans	4,031,000	5,978,000
Interest Income Recognized	214,000	264,000
Real Estate Loans [Member] | Other Commercial Real Estate Loans [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	21,199,000	28,538,000
Recorded Investment With No Allowance	5,903,000	13,642,000
Recorded Investment With Allowance	13,078,000	13,100,000
Total Recorded Investment	18,981,000	26,742,000
Related Allowance	1,310,000	1,942,000
Average Investment in Impaired Loans	22,521,000	30,160,000
Interest Income Recognized	1,198,000	1,332,000
Real Estate Loans [Member] | Total Real Estate [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	30,733,000	39,014,000
Recorded Investment With No Allowance	12,646,000	21,668,000
Recorded Investment With Allowance	15,712,000	15,187,000
Total Recorded Investment	28,358,000	36,855,000
Related Allowance	2,309,000	2,759,000
Average Investment in Impaired Loans	32,018,000	42,896,000
Interest Income Recognized	1,703,000	1,894,000
Commercial Loans [Member] | Commercial [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	842,000	949,000
Recorded Investment With No Allowance	487,000	569,000
Recorded Investment With Allowance	191,000	312,000
Total Recorded Investment	678,000	881,000
Related Allowance	179,000	214,000
Average Investment in Impaired Loans	784,000	1,223,000
Interest Income Recognized	42,000	54,000
Commercial Loans [Member] | Agricultural Loans [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	236,000	572,000
Recorded Investment With No Allowance	74,000	332,000
Recorded Investment With Allowance	16,000	104,000
Total Recorded Investment	90,000	436,000
Related Allowance	24,000	153,000
Average Investment in Impaired Loans	232,000	538,000
Interest Income Recognized	12,000	24,000
Commercial Loans [Member] | Total Commercial [Member] | Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	1,078,000	1,521,000
Recorded Investment With No Allowance	561,000	901,000
Recorded Investment With Allowance	207,000	416,000
Total Recorded Investment	768,000	1,317,000
Related Allowance	203,000	367,000
Average Investment in Impaired Loans	1,016,000	1,761,000
Interest Income Recognized	54,000	78,000
Impaired Loans, Net of Government Guarantees and Excluding Loans Acquired [Member]
Unpaid Contractual Principal Balance	33,498,000	42,499,000
Recorded Investment With No Allowance	14,753,000	24,377,000
Recorded Investment With Allowance	16,050,000	15,731,000
Total Recorded Investment	30,803,000	40,108,000
Related Allowance	2,843,000	3,483,000
Average Investment in Impaired Loans	34,778,000	46,670,000
Interest Income Recognized	$ 1,836,000	$ 2,073,000