Note 12 - Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016		Mar. 31, 2016
Cash and due from banks	$ 190,522,000	$ 218,017,000
Short-term investments	630,058,000	967,067,000
Available-for-sale Securities	1,227,729,000	1,314,345,000	[1]	$ 1,300,000,000
Loans held-for-sale	5,835,000	7,500,000
Loans, net	11,170,158,000	11,006,344,000
Investment in Federal Home Loan Bank stock	17,250,000	17,250,000
Warrants	102,000	79,000
Deposits	11,595,618,000	11,680,017,000
Securities sold under agreements to repurchase	149,982,000	351,989,000
Advances from Federal Home Loan Bank	325,053,000	350,062,000
Other borrowings	15,865,000	15,944,000
Long-term debt	63,076,000	63,169,000
Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	190,522,000	218,017,000
Short-term investments	630,058,000	967,067,000
Available-for-sale Securities	440,570,000	513,376,000	[1]
Loans held-for-sale
Loans, net
Investment in Federal Home Loan Bank stock
Warrants
Deposits
Securities sold under agreements to repurchase
Advances from Federal Home Loan Bank
Other borrowings
Long-term debt
Fair Value, Inputs, Level 2 [Member]
Cash and due from banks
Short-term investments
Available-for-sale Securities	787,159,000	800,969,000	[1]
Loans held-for-sale
Loans, net
Investment in Federal Home Loan Bank stock	17,250,000	17,250,000
Warrants
Deposits
Securities sold under agreements to repurchase	149,982,000	351,989,000
Advances from Federal Home Loan Bank	325,053,000	350,062,000
Other borrowings
Long-term debt	63,076,000	63,169,000
Fair Value, Inputs, Level 3 [Member]
Cash and due from banks
Short-term investments
Available-for-sale Securities			[1]
Loans held-for-sale	5,835,000	7,500,000
Loans, net	11,170,158,000	11,006,344,000
Investment in Federal Home Loan Bank stock
Warrants	102,000	79,000
Deposits	11,595,618,000	11,680,017,000
Securities sold under agreements to repurchase
Advances from Federal Home Loan Bank
Other borrowings	15,865,000	15,944,000
Long-term debt

[1] Preferred stock of government sponsored entities and other equity securities as of December 31, 2015 were reclassified as level 1 rather than level 2 as originally classified due to the availability of quoted prices in active markets.