Note 5 - Loans and Allowance for Loan Losses - Loans by Credit Risk Rating, Segregated by Class of Loans (Details) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Financing Receivables		$ 6,303,351	$ 5,632,890
Loans acquired, net of discount and allowance	[1]	1,092,039	1,305,683
Loans acquired	[1]	1,092,039	1,305,683
Pass [Member]
Financing Receivables		6,140,412	5,433,036
Loans acquired, net of discount and allowance		1,051,889	1,217,886
Loans acquired		1,051,889	1,217,886
Special Mention [Member]
Financing Receivables		32,333	33,865
Loans acquired, net of discount and allowance		9,673	22,181
Loans acquired		9,673	22,181
Substandard [Member]
Financing Receivables		129,662	164,251
Loans acquired, net of discount and allowance		29,862	64,075
Loans acquired		29,862	64,075
Doubtful [Member]
Financing Receivables		944	1,715
Loans acquired, net of discount and allowance		615	1,541
Loans acquired		615	1,541
Unlikely to be Collected Financing Receivable [Member]
Financing Receivables			23
Loans acquired, net of discount and allowance
Loans acquired
Consumer Portfolio Segment [Member]
Financing Receivables		494,262	488,563
Consumer Portfolio Segment [Member] | Pass [Member]
Financing Receivables		490,041	485,575
Consumer Portfolio Segment [Member] | Special Mention [Member]
Financing Receivables			26
Consumer Portfolio Segment [Member] | Substandard [Member]
Financing Receivables		4,221	2,962
Consumer Portfolio Segment [Member] | Doubtful [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member]
Financing Receivables		176,316	184,591
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member] | Pass [Member]
Financing Receivables		176,316	183,943
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member] | Special Mention [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member] | Substandard [Member]
Financing Receivables			648
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member] | Doubtful [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Credit Card Receivable [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivables		317,946	303,972
Consumer Portfolio Segment [Member] | Other Loans [Member] | Pass [Member]
Financing Receivables		313,725	301,632
Consumer Portfolio Segment [Member] | Other Loans [Member] | Special Mention [Member]
Financing Receivables			26
Consumer Portfolio Segment [Member] | Other Loans [Member] | Substandard [Member]
Financing Receivables		4,221	2,314
Consumer Portfolio Segment [Member] | Other Loans [Member] | Doubtful [Member]
Financing Receivables
Consumer Portfolio Segment [Member] | Other Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Real Estate Portfolio Segment [Member]
Financing Receivables		3,794,900	3,028,079
Commercial Real Estate Portfolio Segment [Member] | Pass [Member]
Financing Receivables		3,705,982	2,943,890
Commercial Real Estate Portfolio Segment [Member] | Special Mention [Member]
Financing Receivables		16,367	10,996
Commercial Real Estate Portfolio Segment [Member] | Substandard [Member]
Financing Receivables		72,246	73,019
Commercial Real Estate Portfolio Segment [Member] | Doubtful [Member]
Financing Receivables		305	174
Commercial Real Estate Portfolio Segment [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivables		515,274	336,759
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Pass [Member]
Financing Receivables		507,128	330,080
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Special Mention [Member]
Financing Receivables		2,085	98
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Substandard [Member]
Financing Receivables		6,045	6,565
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Doubtful [Member]
Financing Receivables		16	16
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Financing Receivables		1,048,403	904,245
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Pass [Member]
Financing Receivables		1,022,886	875,603
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Special Mention [Member]
Financing Receivables		2,553	4,024
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Substandard [Member]
Financing Receivables		22,675	24,460
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Doubtful [Member]
Financing Receivables		289	158
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member]
Financing Receivables		2,231,223	1,787,075
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member] | Pass [Member]
Financing Receivables		2,175,968	1,738,207
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member] | Special Mention [Member]
Financing Receivables		11,729	6,874
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member] | Substandard [Member]
Financing Receivables		43,526	41,994
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member] | Doubtful [Member]
Financing Receivables
Commercial Real Estate Portfolio Segment [Member] | Other Commercial Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Portfolio Segment [Member]
Financing Receivables		896,809	789,903
Commercial Portfolio Segment [Member] | Pass [Member]
Financing Receivables		867,159	765,023
Commercial Portfolio Segment [Member] | Special Mention [Member]
Financing Receivables		6,293	662
Commercial Portfolio Segment [Member] | Substandard [Member]
Financing Receivables		23,333	24,195
Commercial Portfolio Segment [Member] | Doubtful [Member]
Financing Receivables		24
Commercial Portfolio Segment [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables			23
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Financing Receivables		688,960	639,525
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Pass [Member]
Financing Receivables		661,635	616,805
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Special Mention [Member]
Financing Receivables		6,267	558
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Substandard [Member]
Financing Receivables		21,057	22,162
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Doubtful [Member]
Financing Receivables		1
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Financing Receivables		207,849	150,378
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Pass [Member]
Financing Receivables		205,524	148,218
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Special Mention [Member]
Financing Receivables		26	104
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Substandard [Member]
Financing Receivables		2,276	2,033
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Doubtful [Member]
Financing Receivables		23
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables			23
Unallocated Financing Receivables [Member]
Financing Receivables		25,341	20,662
Unallocated Financing Receivables [Member] | Pass [Member]
Financing Receivables		25,341	20,662
Unallocated Financing Receivables [Member] | Special Mention [Member]
Financing Receivables
Unallocated Financing Receivables [Member] | Substandard [Member]
Financing Receivables
Unallocated Financing Receivables [Member] | Doubtful [Member]
Financing Receivables
Unallocated Financing Receivables [Member] | Unlikely to be Collected Financing Receivable [Member]
Financing Receivables

[1] See Note 6, Loans Acquired, for segregation of loans acquired by loan class.