Note 5 - Loans Acquired (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Note 5 - Loans Acquired (Details) [Line Items]
Acquired Loans, Covered By FDIC Loss Share Agreements	$ 93,100,000		$ 106,900,000
Allowance for Loan and Lease Losses, Loans Acquired	1,000,000
Certain Loans Acquired In Transfer Accretable Yield Adjustment	15,300,000
FDIC Indemnification Asset Accretable Yield Adjustment	6,600,000
Covered Purchased Impaired Loans, Allowance	1,000,000		1,000,000
Scenario, Forecast [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Certain Loans Acquired In Transfer Accretable Yield Adjustment Current Year Increase Decrease		$ 5,800,000
FDIC Indemnification Asset Accretable Yield Adjustment Current Year Increase Decrease		(5,400,000)
Net Addition to Pre-tax Income Due to Remaining Accretable Yield Adjustments		$ 400,000
Loans Acquired, Not Covered By FDIC Loss Share [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Allowance for Loan and Lease Losses, Loans Acquired	$ 0		$ 0
Liberty Bancshares, Inc. [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Not Covered by FDIC Loss Share				$ 769,900,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross				774,800,000
Loans Acquired Discount				4,900,000
Liberty Bancshares, Inc. [Member] | Purchased Credit Impaired Loans [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Not Covered by FDIC Loss Share				10,700,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross				15,700,000
Loans Acquired Discount				5,000,000
Community First Bancshares, Inc. [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Not Covered by FDIC Loss Share				1,130,000,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross				1,150,000,000
Loans Acquired Discount				23,700,000
Community First Bancshares, Inc. [Member] | Purchased Credit Impaired Loans [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Not Covered by FDIC Loss Share				7,000,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross				10,100,000
Loans Acquired Discount				$ 3,100,000