CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	Total	Shares of Beneficial Interest, $1.00 Par [Member]	Capital Contributed In Excess Of Par [Member]	Accumulated Other Comprehensive Loss [Member]	Distributions in Excess of Net Income [Member]	Non-controlling interest [Member]	Series A [Member]	Series A [Member] Distributions in Excess of Net Income [Member]	Series B [Member]	Series B [Member] Distributions in Excess of Net Income [Member]	Series A Preferred Shares, $25 plus accrued dividends Liquidation Value [Member]	Series B Preferred Shares, $25 plus accrued dividends Liquidation Value [Member]
Beginning Balance at Dec. 31, 2012	$ 713,229	$ 56,331	$ 1,247,730	$ (20,867)	$ (608,634)	$ 38,588					$ 46	$ 35
Net income	25,807				24,802	1,005
Comprehensive income	28,191			2,291		93
Shares issued upon redemption of Operating Partnership units		40	545			(585)
Shares issued under employee and trustee compensation plans, net of shares retired	(1,767)	135	(1,902)
Amortization of deferred compensation	2,213		2,213
Distributions paid to common shareholders ($0.18 per share)	(10,162)				(10,162)
Distributions paid to preferred shareholders							(2,372)	(2,372)	(1,590)	(1,590)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders ($0.18 per unit)	(406)					(406)
Other distributions to noncontrolling interests, net	(266)					(266)
Ending Balance at Mar. 31, 2013	$ 727,070	$ 56,506	$ 1,248,586	$ (18,576)	$ (597,956)	$ 38,429					$ 46	$ 35