Note 5 - Loans Acquired (Details) - Summary of Acquired Loans, Excluding Loans Covered by Loss Share - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	$ 4,853,094	$ 2,736,634
Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4,719,468	2,642,549
Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	17,264	11,938
Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	112,832	80,152
Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	3,526	1,990
Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4	5
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	2,013,816	575,980
Acquired Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,952,157	535,729
Acquired Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8,372	1,435
Acquired Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	51,175	36,957
Acquired Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	2,108	1,854
Acquired Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4	5
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	354,173	288,782
Consumer Portfolio Segment [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	352,790	287,438
Consumer Portfolio Segment [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans		5
Consumer Portfolio Segment [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,345	1,296
Consumer Portfolio Segment [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	38	43
Consumer Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	182,472	103,402
Consumer Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	181,551	102,515
Consumer Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans		5
Consumer Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	883	839
Consumer Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	38	43
Consumer Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	100,080	8,511
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	99,732	8,479
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	32
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	348	0
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	100,080	8,511
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	99,732	8,479
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	32
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	348	0
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,914,409	1,352,328
Commercial Real Estate Portfolio Segment [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,854,496	1,321,194
Commercial Real Estate Portfolio Segment [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	7,409	8,934
Commercial Real Estate Portfolio Segment [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	51,132	22,118
Commercial Real Estate Portfolio Segment [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,372	82
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,037,559	714,797
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	996,692	698,329
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4,869	7,074
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	34,815	9,394
Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,183
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	253,761	181,968
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	247,457	176,825
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	476	84
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	5,812	5,059
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	16
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	623,089	455,563
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	610,347	446,040
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	2,064	1,776
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	10,505	7,665
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	173	82
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,723,164	516,108
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,670,778	480,635
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8,239	1,366
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	42,404	32,248
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,739	1,854
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4	5
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	988,831	334,168
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	957,247	317,965
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	6,370	605
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	25,214	15,598
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	116,302	36,847
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	109,987	27,430
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	78	78
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	6,237	9,339
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	618,031	145,093
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	603,543	135,240
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,791	683
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	10,953	7,311
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,739	1,854
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	4	5
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	564,679	407,478
Commercial Portfolio Segment [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	554,008	386,123
Commercial Portfolio Segment [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	2,074	1,564
Commercial Portfolio Segment [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	9,180	19,780
Commercial Portfolio Segment [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8	11
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	394,422	291,820
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	384,393	271,017
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	1,483	1,544
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8,538	19,248
Commercial Portfolio Segment [Member] | Commercial Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8	11
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	170,257	115,658
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	169,615	115,106
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans		20
Commercial Portfolio Segment [Member] | Agricultural Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	642	532
Commercial Portfolio Segment [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	190,572	51,361
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	181,647	46,615
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	133	69
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8,771	4,677
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	21	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	164,942	47,261
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	156,319	43,585
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	133	69
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	8,469	3,607
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	21	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	25,630	4,100
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	25,328	3,030
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	302	1,070
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0	0
Unallocated Financing Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	6,017	5,133
Unallocated Financing Receivables [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	6,017	$ 5,133
Unallocated Financing Receivables [Member] | Acquired Loans [Member] | Risk Rate 1-4 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0
Unallocated Financing Receivables [Member] | Acquired Loans [Member] | Risk Rate 5 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0
Unallocated Financing Receivables [Member] | Acquired Loans [Member] | Risk Rate 6 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0
Unallocated Financing Receivables [Member] | Acquired Loans [Member] | Risk Rate 7 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	0
Unallocated Financing Receivables [Member] | Acquired Loans [Member] | Risk Rate 8 [Member]
Financing Receivable, Recorded Investment [Line Items]
Acquired loans	$ 0