Note 12 - Preferred Stock (Details Textual) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Apr. 30, 2021	Mar. 31, 2024	Dec. 31, 2023	[1]
Preferred Stock, Shares Issued (in shares)		1,500	1,500
Preferred Stock, Par or Stated Value Per Share (in dollars per share)		$ 1	$ 1
Series 2021 Fixed-Rate Noncumulative Preferred Stock [Member]
Preferred Stock, Shares Issued (in shares)	1,500
Preferred Stock, Value, Outstanding	$ 15
Preferred Stock, Par or Stated Value Per Share (in dollars per share)	$ 1
Preferred Stock, Liquidation Preference Per Share (in dollars per share)	$ 10,000
Preferred Stock, Dividend Rate, Percentage	6.00%

[1] Derived from audited consolidated financial statements.