CONSOLIDATED STATEMENTS OF EQUITY - 9 months ended Sep. 30, 2017 - USD ($) $ in Thousands	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 B [Member]	Series B [Member] Distributions in Excess of Net Income [Member]	Series C [Member]	Series A [Member]	Series A [Member] Distributions in Excess of Net Income [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]	Series C Preferred Stock [Member]	Series D Preferred Stock [Member]
December 31, 2016 at Dec. 31, 2016	$ 702,406	$ 69,553	$ 1,481,787	$ 1,622	$ (997,789)	$ 147,152						$ 46	$ 35
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(41,463)					(4,416)
Net Income (Loss), Excluding Portion Attributable to Noncontrolling Interest					(37,047)
Other comprehensive income	2,141			1,912		229
Shares issued under employee compensation plans, net of shares retired	462	314	148
Amortization of deferred compensation	4,518		4,518
Distributions paid to common shareholders ($0.63 per share)	(43,959)				(43,959)
Distributions paid to preferred shareholders							$ (4,770)	$ (4,770)	$ (7,866)	$ (7,116)	$ (7,116)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders ($0.63 per unit)	(5,232)					(5,232)
September 30, 2017 at Sep. 30, 2017	881,114	69,888	1,768,540	$ 3,534	$ (1,098,547)	137,501						$ 46	$ 35	$ 69	$ 48
Noncontrolling interests:
Stock Issued During Period, Value, New Issues	282,005		281,888											$ 69	$ 48
Shares Issued Upon Redemption Of Operating Partnership Units		$ 21	$ 199			(220)
Other Minority Interest Decrease From Distributions To Noncontrolling Interest Holders	$ (12)					$ (12)