Note 16 - Fair Value of Financial Instruments - Fair Value Hierarchy of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cash and due from banks	$ 247,056	$ 218,017
Short-term investments	292,745	967,067
Securities available-for-sale	1,333,626	1,314,345
Loans held-for-sale	8,000	7,500
Loans, net	12,663,049	11,006,344
Investment in Federal Home Loan Bank stock	23,085	17,250
Warrants	5,218	938
Deposits	12,700,674	11,680,017
Securities sold under agreement to repurchase	100,163	351,989
Advances from Federal Home Loan Bank	429,482	350,062
Other borrowings	51,075	15,944
Long-term debt	141,865	63,169
Warrants [Member]
Warrants	91
Warrants		79
Fair Value, Inputs, Level 1 [Member]
Cash and due from banks	247,056	218,017
Short-term investments	292,745	967,067
Securities available-for-sale	277,622	513,376
Loans held-for-sale
Loans, net
Investment in Federal Home Loan Bank stock
Deposits
Securities sold under agreement to repurchase
Advances from Federal Home Loan Bank
Other borrowings
Long-term debt
Fair Value, Inputs, Level 1 [Member] \| Warrants [Member]
Warrants
Warrants
Fair Value, Inputs, Level 2 [Member]
Cash and due from banks
Short-term investments
Securities available-for-sale	1,056,004	800,969
Loans held-for-sale
Loans, net
Investment in Federal Home Loan Bank stock	23,085	17,250
Deposits
Securities sold under agreement to repurchase	100,163	351,989
Advances from Federal Home Loan Bank	429,482	350,062
Other borrowings
Long-term debt	141,865	63,169
Fair Value, Inputs, Level 2 [Member] \| Warrants [Member]
Warrants
Warrants
Fair Value, Inputs, Level 3 [Member]
Cash and due from banks
Short-term investments
Securities available-for-sale
Loans held-for-sale	8,000	7,500
Loans, net	12,663,049	11,006,344
Investment in Federal Home Loan Bank stock
Deposits	12,700,674	11,680,017
Securities sold under agreement to repurchase
Advances from Federal Home Loan Bank
Other borrowings	51,075	15,944
Long-term debt
Fair Value, Inputs, Level 3 [Member] \| Warrants [Member]
Warrants	$ 91
Warrants		$ 79

Fair value portion of other borrowings.

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Warrants, Fair Value Disclosure

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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