Note 16 - Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Cash and due from banks	$ 218,017,000	$ 180,130,000
Short-term investments	967,067,000	536,880,000
Securities available-for-sale	1,314,345,000	1,586,352,000	[1]
Loans held-for-sale	7,500,000	6,676,000
Loans, net	11,006,344,000	9,938,810,000
Investment in Federal Home Loan Bank stock	17,250,000	17,250,000
Warrants	79,000	62,000
Deposits	11,680,017,000	10,509,879,000
Securities sold under agreement to repurchase	351,989,000	413,417,000
Advances from Federal Home Loan Bank	350,062,000	274,488,000
Other borrowings	15,944,000	16,684,000
Long-term debt	63,169,000	58,420,000
Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	218,017,000	180,130,000
Short-term investments	967,067,000	536,880,000
Securities available-for-sale	513,376,000	302,032,000	[1]
Loans held-for-sale
Loans, net
Investment in Federal Home Loan Bank stock
Warrants
Deposits
Securities sold under agreement 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
Securities available-for-sale	800,969,000	1,284,320,000	[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 agreement to repurchase	351,989,000	413,417,000
Advances from Federal Home Loan Bank	350,062,000
Other borrowings
Long-term debt	63,169,000	58,420,000
Fair Value, Inputs, Level 3 [Member]
Cash and due from banks
Short-term investments
Securities available-for-sale			[1]
Loans held-for-sale	7,500,000	6,676,000
Loans, net	11,006,344,000	9,938,810,000
Investment in Federal Home Loan Bank stock
Warrants	79,000	62,000
Deposits	11,680,017,000	10,509,879,000
Securities sold under agreement to repurchase
Advances from Federal Home Loan Bank		274,488,000
Other borrowings	15,944,000	16,684,000
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.