Note 5 - Loans Acquired (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2013
Note 5 - Loans Acquired (Details) [Line Items]
FDIC Indemnification Asset, Cash Payments Received	$ 2,368,000
Gain (Loss) on Contract Termination	(7,476,000)
Non-Covered Impaired Loans Allowance, Reclassified	954,000
Acquired Loans, Covered By FDIC Loss Share Agreements		$ 106,900,000				$ 954,000
Covered Purchased Impaired Loans, Allowance		954,000
Provision for Loan and Lease Losses	9,022,000	$ 7,245,000	$ 4,118,000
FDIC Indemnification Asset, Disposals	7,500,000
Acquired Loans [Member]
Note 5 - Loans Acquired (Details) [Line Items]
Non-Covered Impaired Loans Allowance, Reclassified	954,000
Provision for Loan and Lease Losses	$ 736,000
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
Metropolitan [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			429,000,000		$ 308,200,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross			442,000,000		316,100,000
Loans Acquired Discount			13,000,000		7,900,000
Metropolitan [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			28,400,000		3,500,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed Other Noncurrent Assets Loans Acquired Gross			52,800,000		10,700,000
Loans Acquired Discount			$ 24,500,000		$ 7,200,000