Consolidated Statement of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Distributions in Excess of Net Income [Member]	Non-controlling Interest [Member]
Balance at Dec. 31, 2011	$ 2,779,658	$ 793,910	$ 2,529	$ 3,594,588	$ 987	$ (1,677,328)	$ 64,972
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(18,110)					(17,467)	(643)
Other comprehensive income	519				519
Issuance of common shares	146,437		108	146,329
Stock based compensation plan activity	3,386		4	4,209		(827)
Conversion of Limited Partner Units			23	29,437			(29,460)
Distributions to preferred shareholders	(13,193)					(13,193)
Redemption of preferred shares	(168,272)	(168,272)		5,730		(5,730)
Distributions to common shareholders ($0.17 per share)	(43,922)					(43,922)
Distributions to noncontrolling interests	(1,033)						(1,033)
Balance at Mar. 31, 2012	$ 2,685,470	$ 625,638	$ 2,664	$ 3,780,293	$ 1,506	$ (1,758,467)	$ 33,836