Note 4 - Loans and Allowance for Loan Losses (Detail) - Loans by Credit Risk Rating (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Risk Rate 1-4 [Member] | Credit Cards [Member]
Consumer:
Financing receivables	$ 175,165	$ 189,365
Risk Rate 1-4 [Member] | Student Loans [Member]
Consumer:
Financing receivables	34,117	44,936
Risk Rate 1-4 [Member] | Other Consumer [Member]
Consumer:
Financing receivables	105,777	107,217
Risk Rate 1-4 [Member] | Consumer Loans [Member]
Consumer:
Financing receivables	315,059	341,518
Risk Rate 1-4 [Member] | Construction Loans [Member]
Consumer:
Financing receivables	121,984	100,534
Risk Rate 1-4 [Member] | Single Family Residential Loans [Member]
Consumer:
Financing receivables	348,654	345,880
Risk Rate 1-4 [Member] | Other Commercial Real Estate Loans [Member]
Consumer:
Financing receivables	511,509	491,466
Risk Rate 1-4 [Member] | Real Estate Loans [Member]
Consumer:
Financing receivables	982,147	937,880
Risk Rate 1-4 [Member] | Other Commercial Loans [Member]
Consumer:
Financing receivables	135,936	136,107
Risk Rate 1-4 [Member] | Agricultural Loans [Member]
Consumer:
Financing receivables	130,323	84,747
Risk Rate 1-4 [Member] | Commercial Loans [Member]
Consumer:
Financing receivables	266,259	220,854
Risk Rate 1-4 [Member] | Other Loans [Member]
Consumer:
Financing receivables	3,527	4,728
Risk Rate 1-4 [Member] | Loans Acquired, Covered By FDIC Loss Share [Member]
Consumer:
Financing receivables	163,657	158,075
Risk Rate 1-4 [Member] | Loans Acquired, Not Covered By FDIC Loss Share [Member]
Consumer:
Financing receivables	73,023
Risk Rate 1-4 [Member] | Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	1,803,672
Risk Rate 1-4 [Member] | Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		1,663,055
Risk Rate 5 [Member] | Other Consumer [Member]
Consumer:
Financing receivables	48	12
Risk Rate 5 [Member] | Consumer Loans [Member]
Consumer:
Financing receivables	48	12
Risk Rate 5 [Member] | Construction Loans [Member]
Consumer:
Financing receivables	239	3,699
Risk Rate 5 [Member] | Single Family Residential Loans [Member]
Consumer:
Financing receivables	1,650	1,377
Risk Rate 5 [Member] | Other Commercial Real Estate Loans [Member]
Consumer:
Financing receivables	8,758	8,465
Risk Rate 5 [Member] | Real Estate Loans [Member]
Consumer:
Financing receivables	10,647	13,541
Risk Rate 5 [Member] | Other Commercial Loans [Member]
Consumer:
Financing receivables	166	510
Risk Rate 5 [Member] | Agricultural Loans [Member]
Consumer:
Financing receivables		148
Risk Rate 5 [Member] | Commercial Loans [Member]
Consumer:
Financing receivables	166	658
Risk Rate 5 [Member] | Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	10,861
Risk Rate 5 [Member] | Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		14,211
Risk Rate 6 [Member] | Credit Cards [Member]
Consumer:
Financing receivables	595	605
Risk Rate 6 [Member] | Student Loans [Member]
Consumer:
Financing receivables	2,324	2,483
Risk Rate 6 [Member] | Other Consumer [Member]
Consumer:
Financing receivables	1,720	1,906
Risk Rate 6 [Member] | Consumer Loans [Member]
Consumer:
Financing receivables	4,639	4,994
Risk Rate 6 [Member] | Construction Loans [Member]
Consumer:
Financing receivables	6,200	5,592
Risk Rate 6 [Member] | Single Family Residential Loans [Member]
Consumer:
Financing receivables	5,609	7,821
Risk Rate 6 [Member] | Other Commercial Real Estate Loans [Member]
Consumer:
Financing receivables	25,957	36,441
Risk Rate 6 [Member] | Real Estate Loans [Member]
Consumer:
Financing receivables	37,766	49,854
Risk Rate 6 [Member] | Other Commercial Loans [Member]
Consumer:
Financing receivables	2,612	4,762
Risk Rate 6 [Member] | Agricultural Loans [Member]
Consumer:
Financing receivables	404	833
Risk Rate 6 [Member] | Commercial Loans [Member]
Consumer:
Financing receivables	3,016	5,595
Risk Rate 6 [Member] | Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	45,421
Risk Rate 6 [Member] | Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		60,443
Risk Rate 7 [Member] | Other Consumer [Member]
Consumer:
Financing receivables	36	50
Risk Rate 7 [Member] | Consumer Loans [Member]
Consumer:
Financing receivables	36	50
Risk Rate 7 [Member] | Single Family Residential Loans [Member]
Consumer:
Financing receivables	63	16
Risk Rate 7 [Member] | Real Estate Loans [Member]
Consumer:
Financing receivables	63	16
Risk Rate 7 [Member] | Other Commercial Loans [Member]
Consumer:
Financing receivables	5	43
Risk Rate 7 [Member] | Commercial Loans [Member]
Consumer:
Financing receivables	5	43
Risk Rate 7 [Member] | Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	104
Risk Rate 7 [Member] | Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		109
Risk Rate 8 [Member] | Other Consumer [Member]
Consumer:
Financing receivables	23	26
Risk Rate 8 [Member] | Consumer Loans [Member]
Consumer:
Financing receivables	23	26
Risk Rate 8 [Member] | Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	23
Risk Rate 8 [Member] | Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		26
Credit Cards [Member]
Consumer:
Financing receivables	175,760	189,970
Student Loans [Member]
Consumer:
Financing receivables	36,441	47,419
Other Consumer [Member]
Consumer:
Financing receivables	107,604	109,211
Consumer Loans [Member]
Consumer:
Financing receivables	319,805	346,600
Construction Loans [Member]
Consumer:
Financing receivables	128,423	109,825
Single Family Residential Loans [Member]
Consumer:
Financing receivables	355,976	355,094
Other Commercial Real Estate Loans [Member]
Consumer:
Financing receivables	546,224	536,372
Real Estate Loans [Member]
Consumer:
Financing receivables	1,030,623	1,001,291
Other Commercial Loans [Member]
Consumer:
Financing receivables	138,719	141,422
Agricultural Loans [Member]
Consumer:
Financing receivables	130,727	85,728
Commercial Loans [Member]
Consumer:
Financing receivables	269,446	227,150
Other Loans [Member]
Consumer:
Financing receivables	3,527	4,728
Loans Acquired, Covered By FDIC Loss Share [Member]
Consumer:
Financing receivables	163,657	158,075
Loans Acquired, Not Covered By FDIC Loss Share [Member]
Consumer:
Financing receivables	73,023
Total Loans Includeing Covered Loans [Member]
Consumer:
Financing receivables	1,860,081
Total Loans, Including Loans Acquired [Member]
Consumer:
Financing receivables		$ 1,737,844