Note 14 - Stockholders' Equity - Dividends Declared (Details) - $ / shares		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Common Stock (in dollars per share)		$ 0.28000	$ 0.28000
Series I Preferred Stock [Member]
Preferred Shares (in dollars per share)	[1]	0	0.37500
Series J Preferred Stock [Member]
Preferred Shares (in dollars per share)	[1]	0	0.34375
Series K Preferred Stock [Member]
Preferred Shares (in dollars per share)	[1]	0	0.35156
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

[1] Shares were fully redeemed during 2019