Note 5 - Loans Acquired (Details) - Age Analysis of Past Due Acquired Loans, Excluding Loans Covered by Loss Share - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	$ 4,920,000	$ 2,740,000
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	51,039	15,151
Past due acquired loans, current	1,621,862	560,829
Past due acquired loans, total loans	1,672,901	575,980
Past due acquired loans, 90 days past due and accruing	3,224	599
Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	26,078	5,691
Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	24,961	9,460
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	385,668	288,782
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	208,380	103,402
Consumer Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	948	104
Past due acquired loans, current	74,658	8,407
Past due acquired loans, total loans	75,606	8,511
Past due acquired loans, 90 days past due and accruing	57	5
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	826	70
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	122	34
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	948	104
Past due acquired loans, current	74,658	8,407
Past due acquired loans, total loans	75,606	8,511
Past due acquired loans, 90 days past due and accruing	57	5
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	826	70
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	122	34
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	2,204,992	1,352,328
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	1,229,072	714,797
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	279,740	181,968
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	696,180	455,563
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	45,248	14,516
Past due acquired loans, current	1,386,941	501,592
Past due acquired loans, total loans	1,432,189	516,108
Past due acquired loans, 90 days past due and accruing	1,859	594
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	23,139	5,511
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	22,109	9,005
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	20,720	7,409
Past due acquired loans, current	833,348	326,759
Past due acquired loans, total loans	854,068	334,168
Past due acquired loans, 90 days past due and accruing	203	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	12,910	1,415
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	7,810	5,994
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	10,185	397
Past due acquired loans, current	66,934	36,450
Past due acquired loans, total loans	77,119	36,847
Past due acquired loans, 90 days past due and accruing	410	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	736	292
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	9,449	105
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	14,343	6,710
Past due acquired loans, current	486,659	138,383
Past due acquired loans, total loans	501,002	145,093
Past due acquired loans, 90 days past due and accruing	1,246	594
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	9,493	3,804
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	4,850	2,906
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	648,679	407,478
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	500,116	291,820
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total loans	148,563	115,658
Commercial Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	4,843	531
Past due acquired loans, current	160,263	50,830
Past due acquired loans, total loans	165,106	51,361
Past due acquired loans, 90 days past due and accruing	1,308	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	2,113	110
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	2,730	421
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	4,333	531
Past due acquired loans, current	150,200	46,730
Past due acquired loans, total loans	154,533	47,261
Past due acquired loans, 90 days past due and accruing	912	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	1,999	110
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	2,334	421
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	510	0
Past due acquired loans, current	10,063	4,100
Past due acquired loans, total loans	10,573	4,100
Past due acquired loans, 90 days past due and accruing	396	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	114	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due acquired loans, total past due	$ 396	$ 0