Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans (USD $)	Mar. 31, 2015		Dec. 31, 2014
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans		[1]	$ 682,913,000	[1]
Other Consumer [Member] | Consumer Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	131,168,000		8,514,000
Construction Loans [Member] | Real Estate Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	158,101,000		46,911,000
Single Family Residential Loans [Member] | Real Estate Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	723,658,000		175,970,000
Other Commercial Real Estate Loans [Member] | Real Estate Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	1,162,870,000		390,877,000
Commercial [Member] | Commercial Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	314,723,000		56,134,000
Agricultural Loans [Member] | Commercial Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	23,400,000		4,507,000
Other Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	6,988		60,641,000
Consumer Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	131,168,000		8,514,000
Real Estate Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	2,044,629,000		613,758,000
Commercial Loans [Member]
Note 5 - Loans Acquired (Details) - Carrying Value of all Acquired Impaired Loans [Line Items]
Acquired loans	$ 338,123,000		$ 60,641,000

[1] Loans acquired include $102.5 million and $106.9 million (each net of $1.0 million allowance) of loans covered by FDIC loss share agreements at March 31, 2015 and December 31, 2014, respectively.