Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Operating real estate, accumulated depreciation	$ 2,458,806,000	$ 2,278,292,000
Assets of Consolidated Variable Interest Entities	647,230,000	333,705,000
Liabilities of Consolidated Variable Interest Entities	$ 408,112,000	$ 176,216,000
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	6,017,400	6,029,100
Preferred stock, shares issued (in shares)	32,000	32,000
Preferred stock, shares outstanding (in shares)	32,000	32,000
Preferred stock, aggregate liquidation preference	$ 800,000	$ 800,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	750,000,000	750,000,000
Common stock, shares issued (in shares)	425,633,409	425,034,113
Common stock, shares outstanding (in shares)	425,633,409	425,034,113