NOTE 2 - INVESTMENT SECURITIES (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) item state	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) item state	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) state item
Number of securities | item	647		647
Available-for-sale, unrealized loss positions, qualitative disclosure, number of positions | item	73		73
Aggregate losses of securities (as a percent)	0.30%		0.30%
Available-for-sale, unrealized loss positions, qualitative disclosure, number of positions, greater than or equal to one year	0		0
Other than temporary impairment losses, investments	$ 0	$ 0	$ 0	$ 0
Sale of securities	22,252,000	23,364,000	28,579,000	28,025,000
Gain on sale	$ 1,802,000	$ 143,000	$ 1,936,000	$ 150,000
Number Of Charters Owning Municipal Securities | item			4
Municipal securities | General Obligation Bonds
Number of issuers | item	114		114		93
Other investments	$ 110,300,000		$ 110,300,000		$ 77,200,000
Number of states holding investments | state	21		21		22
Municipal securities | General Obligation Bonds | Minimum
Other investments	$ 5,000,000.0		$ 5,000,000.0		$ 5,000,000.0
Municipal securities | General Obligation Bonds | Aggregate Fair Value Exceeding 5 Million [Member]
Number of states holding investments | state	9		9		6
Municipal securities | Revenue Bonds
Number of issuers | item	182		182		154
Other investments	$ 484,100,000		$ 484,100,000		$ 396,600,000
Number of states holding investments	24		24		17
Municipal securities | Revenue Bonds | Minimum
Other investments	$ 5,000,000.0		$ 5,000,000.0		$ 5,000,000.0
Municipal securities | Revenue Bonds | Aggregate Fair Value Exceeding 5 Million [Member]
Number of states holding investments	13		13		9