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]	Subsidiary of Common Parent [Member]	Subsidiary of Common Parent [Member] Preferred Stock [Member]	Subsidiary of Common Parent [Member] Common Stock [Member]	Subsidiary of Common Parent [Member] Limited Partner [Member]	Subsidiary of Common Parent [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Subsidiary of Common Parent [Member] Non-controlling Interest [Member]	Subsidiary of Common Parent [Member] Stockholders' Equity, Total [Member]
Beginning Balance - Partnership at Dec. 31, 2009								$ 2,967,666	$ 1,016,625	$ 1,918,329	$ 31,192	$ (5,630)	$ 7,150	$ 2,960,516
Beginning Balance - General Partner at Dec. 31, 2009	2,967,860	1,016,625	2,240	3,267,196	(5,630)	(1,355,086)	42,515
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	65,262					65,798	(536)	65,262	69,468	(3,670)	(351)		(185)	65,447
Other comprehensive income	4,198				4,198			4,198				4,198		4,198
Issuance of common shares	298,066		265	297,801
Capital Contribution from the General Partner								298,066		298,066				298,066
Issuance of Limited Partner Units for acquisition	0							0
Stock based compensation plan activity	10,528		3	13,056		(2,531)		10,528		10,528				10,528
Conversion of Limited Partner Units			14	(8,069)		0	8,055			(8,055)	8,055
Distributions to preferred shareholders	(69,468)					(69,468)		(69,468)	(69,468)					(69,468)
Redemption/repurchase of preferred shares	(118,787)	(112,085)		3,736		(10,438)		(118,787)	(112,085)	(6,702)				(118,787)
Distributions to common shareholders	(162,015)					(162,015)
Distribution to Partners								(165,881)		(161,879)	(4,002)			(165,881)
Contributions from noncontrolling interests, net	(5,741)						(5,741)	(1,739)					(1,739)
Buyout of noncontrolling interests	0							0
Ending Balance - Partnership at Dec. 31, 2010								2,989,845	904,540	2,046,617	34,894	(1,432)	5,226	2,984,619
Ending Balance - General Partner at Dec. 31, 2010	2,989,903	904,540	2,522	3,573,720	(1,432)	(1,533,740)	44,293
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	96,309					95,565	744	96,309	60,353	35,212	859		(115)	96,424
Other comprehensive income	2,419				2,419			2,419				2,419		2,419
Issuance of Limited Partner Units for acquisition	28,357		0	0			28,357	28,357			28,357			28,357
Stock based compensation plan activity	10,855		4	14,041		(3,190)		10,890		10,890				10,890
Conversion of Limited Partner Units			3	3,127			(3,130)			3,130	(3,130)
Distributions to preferred shareholders	(60,353)					(60,353)		(60,353)	(60,353)					(60,353)
Redemption/repurchase of preferred shares	(110,726)	(110,630)		3,700		(3,796)		(110,726)	(110,630)	(96)				(110,726)
Distributions to common shareholders	(171,814)					(171,814)
Distribution to Partners								(176,593)		(171,867)	(4,726)			(176,593)
Contributions from noncontrolling interests, net	(5,292)						(5,292)	(566)					(566)
Buyout of noncontrolling interests	0							0
Ending Balance - Partnership at Dec. 31, 2011								2,779,582	793,910	1,923,886	56,254	987	4,545	2,775,037
Ending Balance - General Partner 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 income (loss)	(75,868)					(73,977)	(1,891)	(75,868)	46,438	(120,415)	(2,273)		382	(76,250)
Other comprehensive income	1,704				1,704			1,704				1,704		1,704
Issuance of common shares	314,823		227	314,596
Capital Contribution from the General Partner								314,823		314,823				314,823
Issuance of Limited Partner Units for acquisition	0						0	0
Stock based compensation plan activity	6,432		13	9,395		(2,976)		6,457		6,457				6,457
Conversion of Limited Partner Units			25	29,188			(29,213)			29,213	(29,213)
Distributions to preferred shareholders	(46,438)					(46,438)		(46,438)	(46,438)					(46,438)
Redemption/repurchase of preferred shares	(168,272)	(168,272)		5,730		(5,730)		(168,272)	(168,272)					(168,272)
Distributions to common shareholders	(181,892)					(181,892)
Distribution to Partners								(185,299)		(182,008)	(3,291)			(185,299)
Contributions from noncontrolling interests, net	2,179						2,179	5,470					5,470
Buyout of noncontrolling interests	(6,208)					(4,865)	(1,343)	(6,208)		(4,865)	(94)		(1,249)	(4,959)
Ending Balance - Partnership at Dec. 31, 2012								2,625,951	625,638	1,967,091	21,383	2,691	9,148	2,616,803
Ending Balance - General Partner at Dec. 31, 2012	$ 2,626,118	$ 625,638	$ 2,794	$ 3,953,497	$ 2,691	$ (1,993,206)	$ 34,704