Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Real estate, accumulated depreciation	$ 2,393,946	$ 2,385,287
Assets of consolidated variable interest entities	241,538	239,012
Liabilities of consolidated variable interest entities	$ 140,769	$ 143,186
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	5,996,240	5,996,240
Preferred stock, shares issued (in shares)	42,580	42,580
Preferred stock, shares outstanding (in shares)	42,580	42,580
Preferred stock, liquidation preference	$ 1,064,500	$ 1,064,500
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)	422,037,132	421,388,879
Common stock, shares outstanding (in shares)	422,037,132	421,388,879