Note 15 - Stockholders' Equity - Dividends Declared (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Common Shares (in dollars per share)	$ 0.17000	$ 0	$ 0.34000	$ 0.28000
Series L Preferred Stock [Member]
Preferred Shares (in dollars per share)	0.32031	0.32031	0.64062	0.64062
Series M Preferred Stock [Member]
Preferred Shares (in dollars per share)	$ 0.32813	$ 0.32813	$ 0.65626	$ 0.65626