Consolidated Statement of Changes in Equity (USD $) In Thousands	Parent Company [Member]	Partnership Interest [Member]	Preferred Stock [Member] Parent Company [Member]	Common Stock [Member] Parent Company [Member]	Treasury Stock [Member] Parent Company [Member]	Additional Paid-in Capital [Member] Parent Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Parent Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Partnership Interest [Member]	Distributions in Excess of Net Income [Member] Parent Company [Member]	Total Stockholders' Equity [Member] Parent Company [Member]	Noncontrolling Interests Preferred Units [Member] Parent Company [Member]	Noncontrolling Interest Exchangeable Operating Partnership Units [Member] Parent Company [Member]	Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member] Parent Company [Member]	Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member] Partnership Interest [Member]	Total Noncontrolling Interests [Member] Parent Company [Member]	Preferred Units [Member] Partnership Interest [Member]	General Partner Preferred and Common Units [Member] Partnership Interest [Member]	Limited Partners [Member] Partnership Interest [Member]	Total Partners' Capital [Member] Partnership Interest [Member]	Preferred Units [Member] Partnership Interest [Member]	Preferred Units [Member] Accumulated Other Comprehensive Income (Loss) [Member] Partnership Interest [Member]	Preferred Units [Member] Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member] Partnership Interest [Member]	Preferred Units [Member] Partnership Interest [Member]	Preferred Units [Member] General Partner Preferred and Common Units [Member] Partnership Interest [Member]	Preferred Units [Member] Limited Partners [Member] Partnership Interest [Member]	Preferred Units [Member] Total Partners' Capital [Member] Partnership Interest [Member]	Preferred Stock [Member] Parent Company [Member]	Preferred Stock [Member] Parent Company [Member]	Preferred Stock [Member] Common Stock [Member] Parent Company [Member]	Preferred Stock [Member] Treasury Stock [Member] Parent Company [Member]	Preferred Stock [Member] Additional Paid-in Capital [Member] Parent Company [Member]	Preferred Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member] Parent Company [Member]	Preferred Stock [Member] Distributions in Excess of Net Income [Member] Parent Company [Member]	Preferred Stock [Member] Total Stockholders' Equity [Member] Parent Company [Member]	Preferred Stock [Member] Noncontrolling Interests Preferred Units [Member] Parent Company [Member]	Preferred Stock [Member] Noncontrolling Interest Exchangeable Operating Partnership Units [Member] Parent Company [Member]	Preferred Stock [Member] Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member] Parent Company [Member]	Preferred Stock [Member] Total Noncontrolling Interests [Member] Parent Company [Member]	Common Stock [Member] Parent Company [Member]	Common Stock [Member] Preferred Stock [Member] Parent Company [Member]	Common Stock [Member] Parent Company [Member]	Common Stock [Member] Treasury Stock [Member] Parent Company [Member]	Common Stock [Member] Additional Paid-in Capital [Member] Parent Company [Member]	Common Stock [Member] Accumulated Other Comprehensive Income (Loss) [Member] Parent Company [Member]	Common Stock [Member] Distributions in Excess of Net Income [Member] Parent Company [Member]	Common Stock [Member] Total Stockholders' Equity [Member] Parent Company [Member]	Common Stock [Member] Noncontrolling Interests Preferred Units [Member] Parent Company [Member]	Common Stock [Member] Noncontrolling Interest Exchangeable Operating Partnership Units [Member] Parent Company [Member]	Common Stock [Member] Noncontrolling Interests in Limited Partners' Interest in Consolidated Partnerships [Member] Parent Company [Member]	Common Stock [Member] Total Noncontrolling Interests [Member] Parent Company [Member]	Noncontrolling Interests Preferred Units [Member] Parent Company [Member]	Noncontrolling Interest Exchangeable Operating Partnership Units [Member] Parent Company [Member]	Noncontrolling Interest Exchangeable Operating Partnership Units [Member] Total Noncontrolling Interests [Member] Parent Company [Member]
Beginning balance at Dec. 31, 2011	$ 1,869,654	$ 1,869,654	$ 275,000	$ 899	$ (15,197)	$ 2,281,817		$ (71,429)	$ (71,429)	$ (662,735)	$ 1,808,355	$ 49,158	$ (963)	$ 13,104	$ 13,104	$ 61,299	$ 49,158	$ 1,879,784	$ (963)	$ 1,856,550
Net income	38,083	38,083	0	0	0	0		0	0		38,211	(629)	77	424	424	(128)	(629)	38,211	77	37,659
Net Income (Loss) Attributable to Parent	(38,211)	(37,659)
Other comprehensive income (loss)	(4,682)	(4,682)	0	0	0	0		(4,698)	(4,698)	0	(4,698)	0	(9)	25			0	0	(9)	(4,707)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	(144)	399
Other comprehensive income (loss) attributable to noncontrolling interests	(16)	(25)
Deferred compensation plan, net	0		0	0	405	(405)		0		0	0	0	0	0		0
Amortization of restricted stock issued	5,726	5,726	0	0	0	5,726		0	0	0	5,726	0	0	0	0	0	0	5,726	0	5,726
Common stock redeemed for taxes withheld for stock based compensation, net																																								(1,548)	0	0	0	(1,548)	0	0	(1,548)	0	0	0	0
Common stock issued for dividend reinvestment plan																																								495	0	0	0	495	0	0	495	0	0	0	0
Redemption of preferred units	(48,125)		0	0	0	0		0		0	0	(48,125)	0	0		(48,125)
Preferred unit distributions		(12,744)							0						0		404	12,340	0	(12,744)
Stock issued for stock offerings, net of issuance costs		241,386							0						0		0	241,386	0	241,386									250,000	0	0	(8,614)	0	0	241,386	0	0	0	0
Net proceeds from issuance of preferred stock		241,386																										(241,386)
Redemption of preferred stock	(200,000)		(200,000)	0	0	6,993		0		(6,993)	(200,000)	0	0	0		0
Contributions from partners	3,317	3,317	0	0	0	0		0	0	0	0	0	0	3,317	3,317	3,317	0	0	0	0
Distributions to partners	(576)	(83,327)	0	0	0	0		0	0	0	0	0	0	(576)	576	(576)	0	82,587	164	(82,751)
Preferred stock redemptions																					(248,125)	0	0	48,125	200,000	0	(248,125)
Common units issued as a result of common stock issued by Parent Company, net of repurchases		(1,053)							0						0		0	1,053	0	(1,053)
Preferred stock/unit	(12,744)		0	0	0	0		0		(12,340)	(12,340)		0	0		(404)																																				404
Preferred stock dividends	(19,333)
Common stock/unit	(82,751)		0	0	0	0		0		(82,587)	(82,587)	0		0		(164)																																					164
Ending Balance at Jun. 30, 2012	1,817,599	1,817,599	325,000	899	(14,792)	2,284,464		(66,731)	(66,731)	(726,444)	1,802,396	0	(1,041)	16,244	16,244	15,203	0	1,869,127	(1,041)	1,801,355
Beginning balance at Mar. 31, 2012
Net income	11,348	11,348
Net Income (Loss) Attributable to Parent	(11,093)	(11,116)
Other comprehensive income (loss)	(2,347)	(2,347)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	249	222
Other comprehensive income (loss) attributable to noncontrolling interests	(6)	(10)
Preferred stock dividends	(5,396)
Ending Balance at Jun. 30, 2012	1,817,599	1,817,599
Beginning balance at Dec. 31, 2012	1,745,911	1,745,911							(57,715)			0			16,299		0	1,788,480	(1,153)	1,729,612
Net income	58,603	58,603	0	0	0	0		0	0		57,949	0	109	545	545	654	0	57,949	109	58,058
Net Income (Loss) Attributable to Parent	(57,949)	(58,058)
Other comprehensive income (loss)	(26,453)	(26,453)	0	0	0	0	(26,396)	(26,396)	(26,396)	0	(26,396)	0	(50)	(7)			0	0	(50)	(26,446)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	711	552
Other comprehensive income (loss) attributable to noncontrolling interests	57	7
Deferred compensation plan, net	0		0	0	(1,428)	1,428		0		0	0	0	0	0		0
Amortization of restricted stock issued	6,978	6,978	0	0	0	6,978		0	0	0	6,978	0	0	0	0	0	0	6,978	0	6,978
Common stock redeemed for taxes withheld for stock based compensation, net																																								(2,921)	0	0	0	(2,921)	0	0	(2,921)	0	0	0	0
Common stock issued for dividend reinvestment plan																																								578	0	0	0	578	0	0	578	0	0	0	0
Preferred unit distributions		(10,531)							0						0		0	10,531	0	(10,531)
Stock issued for stock offerings, net of issuance costs																													0	0	0	0	0	0	0	0	0	0	0	(98,278)	0	19	0	98,259	0	0	98,278	0	0	0	0
Net proceeds from issuance of preferred stock		0																										0
Contributions from partners	39	39	0	0	0	0		0	0	0	0	0	0	39	39	39	0	0	0	0
Distributions to partners	(3,311)	(87,356)	0	0	0	0		0	0	0	0	0	0	(3,311)	3,311	(3,311)	0	83,874	171	(84,045)
Common units issued as a result of common stock issued by Parent Company, net of repurchases		95,935							0						0		0	(95,935)	0	95,935
Preferred stock/unit	(10,531)		0	0	0	0		0			(10,531)		0	0		0																																				0
Preferred stock dividends	(10,531)
Common stock/unit	(84,045)		0	0	0	0		0		(83,874)	(83,874)	0	(171)	0																																								171
Ending Balance at Jun. 30, 2013	1,836,032	1,836,032	325,000	923	(16,352)	2,416,632		(31,319)	(31,319)	(871,266)	1,823,618	0	(1,165)	13,579	13,579	12,414	0	1,854,937	(1,165)	1,822,453
Beginning balance at Mar. 31, 2013
Net income	37,469	37,469
Net Income (Loss) Attributable to Parent	(37,129)	(37,199)
Other comprehensive income (loss)	(20,706)	(20,706)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	383	274
Other comprehensive income (loss) attributable to noncontrolling interests	43	4
Preferred stock dividends	(5,265)
Ending Balance at Jun. 30, 2013	$ 1,836,032	$ 1,836,032