Note 3 - Investment Securities (Details Textual)			3 Months Ended
		May 31, 2021 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Mar. 07, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt Securities, Held-to-Maturity, Number of Securities			0
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Ending Balance			$ 0			$ 0
Debt Securities, Held-to-Maturity, Nonaccrual			0
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss			$ 771,000			$ 0
Debt Securities, Available-for-sale, Number of Positions Sold			3
Proceeds from Sale of Debt Securities, Available-for-sale		$ 91,000,000	$ 2,111,000	$ 0
Debt Securities, Available-for-Sale, Gain (Loss), Total			(92,000)
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Ending Balance			$ 0
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions			448			227
Collateral Pledged [Member]
Debt Securities, Available-for-Sale, Restricted			$ 1,100,000			$ 879,000,000
Commonwealth [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities	[1]				$ 246,793,000
Other Assets [Member]
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Total			3,000,000			$ 3,000,000
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss			$ 1,000,000

[1] As of acquisition date, securities with a fair value of $162 million were classified as HTM.