Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Operating real estate, consolidated variable interest entities	$ 1,703,069	$ 1,703,069	$ 1,701,804
Construction-in-progress, consolidated variable interest entities	78,633	78,633	51,313
Accumulated depreciation and amortization, consolidated variable interest entities	312,416	312,416	292,374
Mortgages payable, consolidated variable interest entities	$ 441,469	$ 441,469	$ 444,388
Preferred shares, authorized	15,000,000	15,000,000	15,000,000
Preferred shares, par value	$ 0.01	$ 0.01	$ 0.01
Common shares of beneficial interest, par value	$ 0.01	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized	100,000,000	100,000,000	100,000,000
Common shares of beneficial interest, shares issued	74,950,197	74,950,197	74,249,633
Common shares of beneficial interest, shares outstanding	74,950,197	74,950,197	74,249,633
5.417% Series 1 Cumulative Convertible Preferred
Preferred shares, percentage	5.417%	5.417%	5.417%
Preferred shares, liquidation preference	$ 25	$ 25	$ 25
Preferred shares, shares issued	399,896	399,896	399,896
Preferred shares, shares outstanding	399,896	399,896	399,896
5.0% Series C Cumulative Redeemable Preferred
Preferred shares, percentage		5.00%	5.00%
Preferred shares, liquidation preference	$ 25,000	$ 25,000	$ 25,000
Preferred shares, shares issued	6,000	6,000	6,000
Preferred shares, shares outstanding	6,000	6,000	6,000