Note 18 - Preferred Stock, Common Stock and Convertible Unit Transactions - Preferred Stock Repurchased (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Shares repurchased (in shares)	761,149	567,450	1,084,953
Purchase price	$ 1,491,000	$ 3,441,000	$ (0)
Class L Cumulative Redeemable Preferred Stock Depositary Shares[Member]
Shares repurchased (in shares)	43,777
Purchase price	$ 973,400
Class M Cumulative Redeemable Preferred Stock Depositary Shares [Member]
Shares repurchased (in shares)	23,791
Purchase price	$ 515,900