Note 2 - INVESTMENT SECURITIES (Details) $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($) issuer item state	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) state issuer item
Number of securities \| item	649
Available-for-sale, unrealized loss positions, qualitative disclosure, number of positions \| item	286
Aggregate losses of securities (as a percent)	3.07%
Available-for-sale, unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year \| item	19
Number Of Charters Owning Municipal Securities \| item	4
Proceeds from sale of securities \| $	$ 0.0	$ 19.5
Gains or losses from sale of securities \| $	$ 0.0	$ 0.0
Revenue Bonds
Number of issuers \| issuer	2		2
Percentage threshold	5.00%		5.00%
Municipal securities \| General Obligation Bonds
Number of issuers \| item	113		113
Other investments \| $	$ 112.5		$ 114.5
Number of states holding investments \| state	22		20
Municipal securities \| General Obligation Bonds \| Minimum
Other investments \| $	$ 5.0		$ 5.0
Municipal securities \| General Obligation Bonds \| Aggregate Fair Value Exceeding 5 Million [Member]
Number of states holding investments \| state	7		7
Municipal securities \| Revenue Bonds
Number of issuers \| item	174		165
Other investments \| $	$ 562.3		$ 575.0
Number of states holding investments	28		28
Municipal securities \| Revenue Bonds \| Minimum
Other investments \| $	$ 5.0		$ 5.0
Municipal securities \| Revenue Bonds \| Aggregate Fair Value Exceeding 5 Million [Member]
Number of states holding investments	14		13

The aggregate depreciation from amortized cost basis as a percent.

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The number of the company's that own the company's municipal securities.

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Number of issuers of debt securities.

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Number of securities.

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Represents the number of states investments are held in.

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Percentage threshold of stockholders' equity which general obligation or revenue bonds market value of any single issuer does not exceed.

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- Definition

Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without an allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

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Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount of gain (loss) on sale of investment in debt security measured at amortized cost (held-to-maturity), including other-than-temporary impairment (OTTI).

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Paragraph 2
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- Definition

The cash inflow associated with the sale of securities that had been designated as held-to-maturity. Excludes proceeds from maturities, prepayments and calls by the issuer.

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