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) 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, 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) income	(16,223)				(14,535)	(1,688)
Other comprehensive income (loss)	(6,506)			(5,941)		(565)
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	(14,930)				(14,930)
Dividends paid to preferred shareholders							$ (1,590)		$ (1,590)	$ (3,105)		$ (3,105)	$ (2,148)		$ (2,148)
Shares issued upon redemption of Operating Partnership units		6,250	89,736			(95,986)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders	(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
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) income	2,413
Ending balance at Sep. 30, 2019	462,490	77,602	1,765,900	(15,388)	(1,370,365)	4,587		35			69			50
Beginning balance at Mar. 31, 2019	501,947	77,383	1,761,736	(533)	(1,342,626)	5,833		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(6,080)				(5,751)	(329)
Other comprehensive income (loss)	(11,647)			(11,342)		(305)
Shares issued under employee compensation plans, net of shares retired	337	164	173
Amortization of deferred compensation	1,889		1,889
Dividends paid to common shareholders	(16,278)				(16,278)
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	(464)					(464)
Other changes in noncontrolling interest, net	(10)					(10)
Ending balance at Jun. 30, 2019	462,850	77,547	1,763,798	(11,875)	(1,371,499)	4,725		35			69			50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	24,716				24,262	454
Other comprehensive income (loss)	(3,604)			(3,513)		(91)
Shares issued under employee compensation plans, net of shares retired	335	55	280
Amortization of deferred compensation	1,822		1,822
Dividends paid to common shareholders	(16,284)				(16,284)
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	(425)					(425)
Other changes in noncontrolling interest, net	(76)					(76)
Ending balance at Sep. 30, 2019	462,490	77,602	1,765,900	(15,388)	(1,370,365)	4,587		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) income	(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) income	(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) income	(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) income	(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