Note 17 - Preferred Stock, Common Stock and Convertible Unit Transactions - Dividends Declared (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common Stock (in dollars per share)	$ 0.54000	$ 1.12000	$ 1.12000
Series I Preferred Stock [Member]
Preferred Shares (in dollars per share)	0	0.99583	1.50000
Series J Preferred Stock [Member]
Preferred Shares (in dollars per share)	0	1.37500	1.37500
Series K Preferred Stock [Member]
Preferred Shares (in dollars per share)	0	0.93359	1.40625
Series L Preferred Stock [Member]
Preferred Shares (in dollars per share)	1.28125	1.28125	1.28125
Series M Preferred Stock [Member]
Preferred Shares (in dollars per share)	$ 1.31250	$ 1.31250	$ 1.31250