CONSOLIDATED STATEMENTS OF EQUITY - 6 months ended Jun. 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 Shares, $25 plus accrued dividends Liquidation Value [Member]	Series B Preferred Shares, $25 plus accrued dividends Liquidation Value [Member]	Preferred Class C [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	(53,763)					(5,721)
Net Income (Loss), Excluding Portion Attributable to Noncontrolling Interest					(48,042)
Other comprehensive income	1,616			1,443		173
Shares issued under employee compensation plans, net of shares retired	(145)	256	(401)
Amortization of deferred compensation	3,119		3,119
Distributions paid to common shareholders ($0.42 per share)	(29,291)				(29,291)
Distributions paid to preferred shareholders							$ (3,180)	$ (3,180)	$ (4,763)	$ (4,744)	$ (4,744)
Noncontrolling interests:
Distributions paid to Operating Partnership unit holders ($0.42 per unit)	(3,491)					(3,491)
June 30, 2017 at Jun. 30, 2017	774,074	$ 69,809	1,650,746	$ 3,065	$ (1,087,809)	$ 138,113						$ 46	$ 35	$ 69
Noncontrolling interests:
Stock Issued During Period, Value, New Issues	$ 166,310		$ 166,241											$ 69