Note 15 - Stockholders' Equity - Dividends Declared (Details) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Common Shares (in dollars per share)	$ 0.17000	$ 0.28000
Series L Preferred Stock [Member]
Preferred Shares (in dollars per share)	0.32031	0.32031
Series M Preferred Stock [Member]
Preferred Shares (in dollars per share)	$ 0.32813	$ 0.32813