Note 6 - Loans Acquired - Age Analysis of Past Due Acquired Loans, Excluding Loans Covered by Loss Share (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Loans	$ 6,303,000,000	$ 5,633,000,000
Acquired Loans [Member]
Past Due	15,391,000	37,940,000
Current	1,076,648,000	1,267,743,000
Loans	1,092,039,000	1,305,683,000
90 Days Past Due & Accruing	7,000	11,000
Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	6,183,000	12,668,000
Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	9,208,000	25,272,000
Consumer Portfolio Segment [Member]
Loans	494,262,000	488,563,000
Consumer Portfolio Segment [Member] | Other Loans [Member]
Loans	317,946,000	303,972,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member]
Past Due	562,000	760,000
Current	29,100,000	48,917,000
Loans	29,662,000	49,677,000
90 Days Past Due & Accruing	7,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	401,000	571,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	161,000	189,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Past Due	562,000	760,000
Current	29,100,000	48,917,000
Loans	29,662,000	49,677,000
90 Days Past Due & Accruing	7,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	401,000	571,000
Consumer Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	161,000	189,000
Commercial Real Estate Portfolio Segment [Member]
Loans	3,794,900,000	3,028,079,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Loans	515,274,000	336,759,000
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Loans	1,048,403,000	904,245,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member]
Past Due	12,827,000	34,256,000
Current	965,482,000	1,136,615,000
Loans	978,309,000	1,170,871,000
90 Days Past Due & Accruing		11,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	5,610,000	11,326,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	7,217,000	22,930,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member]
Past Due	3,476,000	13,577,000
Current	562,517,000	676,531,000
Loans	565,993,000	690,108,000
90 Days Past Due & Accruing
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	806,000	2,836,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Other Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	2,670,000	10,741,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member]
Past Due	1,439,000	7,464,000
Current	47,081,000	50,123,000
Loans	48,520,000	57,587,000
90 Days Past Due & Accruing
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	19,000	132,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Construction Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	1,420,000	7,332,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member]
Past Due	7,912,000	13,215,000
Current	355,884,000	409,961,000
Loans	363,796,000	423,176,000
90 Days Past Due & Accruing		11,000
Commercial Real Estate Portfolio Segment [Member] | Acquired Loans [Member] | Single Family Residential Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	4,785,000	8,358,000
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]
Past Due	3,127,000	4,857,000
Commercial Portfolio Segment [Member]
Loans	896,809,000	789,903,000
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	688,960,000	639,525,000
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	207,849,000	150,378,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member]
Past Due	2,002,000	2,924,000
Current	82,066,000	82,211,000
Loans	84,068,000	85,135,000
90 Days Past Due & Accruing
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	172,000	771,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	1,830,000	2,153,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member]
Past Due	1,944,000	2,876,000
Current	68,676,000	78,961,000
Loans	70,620,000	81,837,000
90 Days Past Due & Accruing
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	156,000	723,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Commercial Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	1,788,000	2,153,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member]
Past Due	58,000	48,000
Current	13,390,000	3,250,000
Loans	13,448,000	3,298,000
90 Days Past Due & Accruing
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Financing Receivables, 30 to 89 Days Past Due [Member]
Past Due	16,000	48,000
Commercial Portfolio Segment [Member] | Acquired Loans [Member] | Agricultural Loans [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Past Due	$ 42,000