Note 6 - Securities Available-for-Sale and Held-to-Maturity - Credit Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Held to maturity, amortized cost	$ 402,237	$ 406,590
State, County and Municipal [Member]
Held to maturity, amortized cost	92,863	92,840
Moody's, Aaa Rating [Member] | State, County and Municipal [Member]
Held to maturity, amortized cost	16,791	18,096
Moody's, Aa 1 To A3 Rating [Member] | State, County and Municipal [Member]
Held to maturity, amortized cost	41,492	40,174
Not Rated [Member] | State, County and Municipal [Member]
Held to maturity, amortized cost	$ 34,580	$ 34,570