Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Operating real estate, consolidated variable interest entities	$ 2,184,537		$ 2,184,537		$ 1,703,202
Construction-in-progress, consolidated variable interest entities	24,679		24,679		44,896
Accumulated depreciation and amortization, consolidated variable interest entities	359,198		359,198		335,735
Mortgages payable, consolidated variable interest entities	$ 396,732		$ 396,732		$ 413,681
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	77,760,588		77,760,588		76,727,394
Common shares of beneficial interest, shares outstanding	77,760,588		77,760,588		76,727,394
5.417% Series 1 Cumulative Convertible Preferred Shares, (stated at liquidation preference $25 per share), 399,896 shares issued and outstanding
Preferred shares, percentage	5.417%	5.417%	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