Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating real estate, consolidated variable interest entities	$ 1,676,866	$ 1,701,804
Construction-in-progress, consolidated variable interest entities	102,583	51,313
Accumulated depreciation and amortization, consolidated variable interest entities	296,165	292,374
Mortgages payable, consolidated variable interest entities	$ 469,184	$ 444,388
Preferred shares, authorized	15,000,000	15,000,000
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, percentage	5.00%	5.00%
Common shares of beneficial interest, par value	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized	100,000,000	100,000,000
Common shares of beneficial interest, shares issued	75,540,804	74,249,633
Common shares of beneficial interest, shares outstanding	75,540,804	74,249,633
5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 399,896 shares issued and outstanding
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, percentage	5.417%	5.417%
Preferred Shares, liquidation preference per share	$ 25	$ 25
Preferred shares, shares issued	399,896	399,896
Preferred shares, shares outstanding	399,896	399,896
5.0% Series C Cumulative Redeemable Preferred Shares, (stated at liquidation preference $25,000 per share), 6,000 shares issued and outstanding
Preferred shares, par value	$ 0.01	$ 0.01
Preferred shares, percentage	5.00%	5.00%
Preferred Shares, liquidation preference per share	$ 25,000	$ 25,000
Preferred shares, shares issued	6,000	6,000
Preferred shares, shares outstanding	6,000	6,000