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 Loss	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, 2019	$ 427,425	$ 77,550	$ 1,766,883	$ (12,556)	$ (1,408,352)	$ 3,746		$ 35			$ 69			$ 50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(13,549)				(13,033)	(516)
Other comprehensive income (loss)	(19,746)			(19,240)		(506)
Shares issued under employee compensation plans, net of shares retired	(42)	1,290	(1,332)
Amortization of deferred compensation	1,624		1,624
Dividends paid to common shareholders	(16,492)				(16,492)
Dividends paid to preferred shareholders							$ (1,591)		$ (1,591)	$ (3,105)		$ (3,105)	$ (2,148)		$ (2,148)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders	(411)					(411)
Ending balance at Mar. 31, 2020	371,965	78,840	1,767,175	(31,796)	(1,444,721)	2,313		35			69			50
Beginning balance at Dec. 31, 2019	427,425	77,550	1,766,883	(12,556)	(1,408,352)	3,746		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(66,245)
Ending balance at Sep. 30, 2020	318,395	79,490	1,770,070	(27,828)	(1,504,371)	880		35			69			50
Beginning balance at Mar. 31, 2020	371,965	78,840	1,767,175	(31,796)	(1,444,721)	2,313		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(23,119)				(22,374)	(745)
Other comprehensive income (loss)	12			508		(496)
Shares issued under employee compensation plans, net of shares retired	114	620	(506)
Amortization of deferred compensation	1,670		1,670
Dividends paid to common shareholders	(1,589)				(1,589)
Dividends paid to preferred shareholders							$ (1,591)		$ (1,591)	$ (3,105)		$ (3,105)	$ (2,148)		$ (2,148)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders	(40)					(40)
Ending balance at Jun. 30, 2020	342,169	79,460	1,768,339	(31,288)	(1,475,528)	1,032		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(29,577)				(28,843)	(734)
Other comprehensive income (loss)	4,056			3,460		596
Shares issued under employee compensation plans, net of shares retired	34	30	4
Amortization of deferred compensation	1,727		1,727
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders	(14)					(14)
Ending balance at Sep. 30, 2020	318,395	79,490	1,770,070	(27,828)	(1,504,371)	880		35			69			50
Beginning balance at Dec. 31, 2020	126,940	79,537	1,771,777	(20,620)	(1,699,638)	(4,270)		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(43,980)				(42,746)	(1,234)
Other comprehensive income (loss)	2,604			2,540		64
Shares issued under employee compensation plans, net of shares retired	(647)	(277)	(370)
Amortization of deferred compensation	1,321		1,321
Ending balance at Mar. 31, 2021	86,238	79,260	1,772,728	(18,080)	(1,742,384)	(5,440)		35			69			50
Beginning balance at Dec. 31, 2020	126,940	79,537	1,771,777	(20,620)	(1,699,638)	(4,270)		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(107,758)
Ending balance at Sep. 30, 2021	30,002	80,200	1,775,959	(12,876)	(1,804,710)	(8,725)		35			69			50
Beginning balance at Mar. 31, 2021	86,238	79,260	1,772,728	(18,080)	(1,742,384)	(5,440)		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(25,380)				(24,597)	(783)
Other comprehensive income (loss)	2,670			2,605		65
Amortization of deferred compensation	1,149		1,149
Noncontrolling interests:
Other changes in noncontrolling interest, net	38					38
Ending balance at Jun. 30, 2021	64,715	79,260	1,773,877	(15,475)	(1,766,981)	(6,120)		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(38,398)				(37,729)	(669)
Other comprehensive income (loss)	2,638			2,599		39
Shares issued under Operating Partnership units		940	1,035			(1,975)
Amortization of deferred compensation	1,047		1,047
Ending balance at Sep. 30, 2021	$ 30,002	$ 80,200	$ 1,775,959	$ (12,876)	$ (1,804,710)	$ (8,725)		$ 35			$ 69			$ 50