Condensed Consolidated Statements of Changes in Equity (Unaudited) (Parentheticals) - $ / shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Series I Preferred Stock [Member]
Dividends per depository share (in dollars per share)	$ 0.75	$ 0.75
Series J Preferred Stock [Member]
Dividends per depository share (in dollars per share)	0.6875	0.6875
Series K Preferred Stock [Member]
Dividends per depository share (in dollars per share)	0.70312	0.70312
Series L Preferred Stock [Member]
Dividends per depository share (in dollars per share)	0.64062
Series M Preferred Stock [Member]
Dividends per depository share (in dollars per share)	0.65626
Dividends per common share (in dollars per share)	$ 0.56	$ 0.54