CONSOLIDATED STATEMENTS OF EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Shares of Beneficial Interest, $1.00 Par	Capital Contributed in Excess of Par	Accumulated Other Comprehensive Income	Distributions in Excess of Net Income	Non- controlling interest	Series B Preferred Stock	Series B Preferred Stock Preferred Shares $.01 par	Series B Preferred Stock Distributions in Excess of Net Income	Series C Preferred Stock	Series C Preferred Stock Preferred Shares $.01 par	Series C Preferred Stock Distributions in Excess of Net Income	Series D Preferred Stock	Series D Preferred Stock Preferred Shares $.01 par	Series D Preferred Stock Distributions in Excess of Net Income
Beginning balance at Dec. 31, 2017	$ 760,991	$ 69,983	$ 1,663,966	$ 7,226	$ (1,109,469)	$ 129,131		$ 35			$ 69			$ 50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(3,712)				(2,601)	(1,111)
Other comprehensive loss	5,103			4,562		541
Shares issued under employee compensation plans, net of shares retired	(195)	370	(565)
Amortization of deferred compensation	1,924		1,924
Dividends paid to common shareholders ($0.21 per share)	(14,766)				(14,766)
Dividends paid to preferred shareholders							$ (1,590)		$ (1,590)	$ (3,105)		$ (3,105)	$ (2,149)		$ (2,149)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders ($0.21 per unit)	(1,737)					(1,737)
Ending balance at Mar. 31, 2018	740,764	70,353	1,665,325	11,788	(1,133,680)	126,824		35			69			50
Beginning balance at Dec. 31, 2018	546,551	70,495	1,671,042	5,408	(1,306,318)	105,770		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(16,223)				(14,535)	(1,688)
Other comprehensive loss	(6,506)			(5,941)		(565)
Shares issued upon redemption of Operating Partnership units		6,250	89,736			(95,986)
Shares issued under employee compensation plans, net of shares retired	(326)	638	(964)
Amortization of deferred compensation	1,922		1,922
Dividends paid to common shareholders ($0.21 per share)	(14,930)				(14,930)
Dividends paid to preferred shareholders							$ (1,590)		$ (1,590)	$ (3,105)		$ (3,105)	$ (2,148)		$ (2,148)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders ($0.21 per unit)	(1,698)					(1,698)
Ending balance at Mar. 31, 2019	$ 501,947	$ 77,383	$ 1,761,736	$ (533)	$ (1,342,626)	$ 5,833		$ 35			$ 69			$ 50