Consolidated Statement of Changes in Equity (USD $) In Thousands	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, 2010	$ 2,989,903	$ 904,540	$ 2,522	$ 3,573,720	$ (1,432)	$ (1,533,740)	$ 44,293
Comprehensive income:
Net income	36,062					36,594	(532)
Derivative instrument activity	1,925				1,925
Comprehensive income	37,987
Issuance of Limited Partner Units for acquisition	28,357						28,357
Stock based compensation plan activity	8,538		4	10,912		(2,378)
Conversion of Limited Partner Units			3	3,049			(3,052)
Distributions to preferred shareholders	(46,347)					(46,347)
Redemption/repurchase of preferred shares	(110,726)	(110,630)		3,700		(3,796)
Distributions to common shareholders ($0.51 per share)	(128,817)					(128,817)
Distributions to noncontrolling interests	(3,952)						(3,952)
Balance at Sep. 30, 2011	$ 2,774,943	$ 793,910	$ 2,529	$ 3,591,381	$ 493	$ (1,678,484)	$ 65,114