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] 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	$ 275,000	$ 899	$ (15,197)	$ 2,281,817		$ (71,429)		$ (662,735)	$ 1,808,355	$ 49,158	$ (963)	$ 13,104		$ 61,299		$ 1,879,784		$ 1,856,550
Deferred compensation plan, net		12																12		12
Stock issued for stock offerings, net of issuance costs			0	5	0	21,672		0		0	21,677	0	0	0		0
Ending Balance at Mar. 31, 2012
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	57,903	57,903	0	0	0	0		0	0		57,780	(629)	116	636	636	123	(629)	57,780	116	57,267
Net Income (Loss) Attributable to Parent	(57,780)	(57,267)
Other comprehensive income (loss)	(7,031)	(7,031)	0	0	0	0		(7,051)	(7,051)	0	(7,051)	0	(14)	34			0	0	(14)	(7,065)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	103	602
Other comprehensive income (loss) attributable to noncontrolling interests	(20)	(34)
Deferred compensation plan, net	12		0	0	441	(429)		0	0	0	12	0	0	0	0	0	0		0
Amortization of restricted stock issued	8,589	8,589	0	0	0	8,589		0	0	0	8,589	0	0	0	0	0	0	8,589	0	8,589
Common stock redeemed for taxes withheld for stock based compensation, net																																							(1,490)	0	0	0	(1,490)	0	0	(1,490)	0	0	0	0
Common stock issued for dividend reinvestment plan																																							740	0	0	0	740	0	0	740	0	0	0	0
Stock Issued During Period, Value, Conversion of Units	0	0
Redemption of preferred units	(48,125)		0	0	0	0		0		0	0	(48,125)	0	0		(48,125)
Preferred unit distributions		(18,392)							0						0		404	17,988	0	(18,392)
Stock issued for stock offerings, net of issuance costs		313,505							0						0		0	313,505	0	313,505								325,000	0	0	(11,495)	0	0	313,505	0	0	0	0
Net proceeds from issuance of preferred stock	313,505	313,505
Redemption of preferred stock	(275,000)	275,000	(275,000)	0	0	9,277		0	0	(9,277)	(275,000)	0	0	0	0	0	0	275,000	0	275,000
Contributions from partners	3,362	3,362	0	0	0	0		0	0	0	0	0	0	3,362	3,362	3,362	0	0	0	0
Distributions to partners	(892)	(125,032)	0	0	0	0		0	0	0	0	0	0	(892)	892	(892)	0	123,894	246	(124,140)
Preferred stock redemptions																					(48,125)	0	0	48,125	0	0	(48,125)
Common units issued as a result of common stock issued by Parent Company, net of repurchases		20,927							0						0		0	(20,927)	0	20,927
Preferred stock/unit	(18,392)		0	0	0	0		0		(17,988)	(17,988)		0	0		(404)																																			404
Preferred stock dividends	(27,265)
Common stock/unit	(124,140)		0	0	0	0		0		(123,894)	(123,894)	0		0		(246)																																				246
Ending Balance at Sep. 30, 2012	1,814,434	1,814,434	325,000	904	(14,756)	2,308,681		(64,378)	(64,378)	(756,114)	1,799,337	0	(1,079)	16,176	16,176	15,097	0	1,863,715	(1,079)	1,798,258
Beginning balance at Jun. 30, 2012
Net income	19,820	19,820
Net Income (Loss) Attributable to Parent	(19,569)	(19,608)
Other comprehensive income (loss)	(2,349)	(2,349)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	247	203
Other comprehensive income (loss) attributable to noncontrolling interests	(4)	(9)
Preferred stock dividends	(7,932)
Ending Balance at Sep. 30, 2012	1,814,434	1,814,434
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	99,268	99,268	0	0	0	0		0	0		98,213	0	183	872	872	1,055	0	98,213	183	98,396
Net Income (Loss) Attributable to Parent	(98,213)	(98,396)
Other comprehensive income (loss)	(29,348)	(29,348)	0	0	0	0	(29,285)	(29,285)	(29,285)	0	(29,285)	0	(55)	(8)			0	0	(55)	(29,340)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	1,118	880
Other comprehensive income (loss) attributable to noncontrolling interests	63	8
Deferred compensation plan, net	0	0	0	0	(1,616)	1,616		0	0	0	0	0	0	0	0	0	0	0	0	0
Amortization of restricted stock issued	10,600	10,600	0	0	0	10,600		0	0	0	10,600	0	0	0	0	0	0	10,600	0	10,600
Common stock redeemed for taxes withheld for stock based compensation, net																																							(2,927)	0	0	0	(2,927)	0	0	(2,927)	0	0	0	0
Common stock issued for dividend reinvestment plan																																							831	0	0	0	831	0	0	831	0	0	0	0
Stock Issued During Period, Value, Conversion of Units	302	302																																					0	0	0	0	302	0	0	302	0	(302)	0	(302)
Redemption of preferred units	0		0	0	0	0		0		0	0	0	0	0		0
Preferred unit distributions		(15,797)							0						0		0	15,797	0	(15,797)
Stock issued for stock offerings, net of issuance costs																												0	0	0	0	0	0	0	0	0	0	0	(99,753)	0	19	0	99,734	0	0	99,753	0	0	0	0
Net proceeds from issuance of preferred stock	0	0
Redemption of preferred stock	0		0	0	0	0		0		0	0	0	0	0		0
Contributions from partners	347	347	0	0	0	0		0	0	0	0	0	0	347	347	347	0	0	0	0
Distributions to partners	(3,635)	(130,239)	0	0	0	0		0	0	0	0	0	0	(3,635)	3,635	(3,635)	0	126,359	245	(126,604)
Common units issued as a result of common stock issued by Parent Company, net of repurchases		97,657							0						0		0	(97,657)	0	97,657
Preferred stock/unit	(15,797)		0	0	0	0		0			(15,797)		0	0		0																																			0
Preferred stock dividends	(15,797)
Common stock/unit	(126,604)		0	0	0	0		0		(126,359)	(126,359)	0	(245)	0																																							245
Common units exchanged for common stock of the parent company		0							0						0		0	302	(302)	0
Ending Balance at Sep. 30, 2013	1,837,095	1,837,095	325,000	923	(16,540)	2,422,466		(28,430)	(28,430)	(878,753)	1,824,666	0	(1,462)	13,891	13,891	12,429	0	1,853,096	(1,462)	1,823,204
Beginning balance at Jun. 30, 2013
Net income	40,664	40,664
Net Income (Loss) Attributable to Parent	(40,264)	(40,337)
Other comprehensive income (loss)	(2,896)	(2,896)
Comprehensive (Income) Loss, Net of Tax, Attributable to Noncontrolling Interest	406	328
Other comprehensive income (loss) attributable to noncontrolling interests	6	1
Preferred stock dividends	(5,266)
Ending Balance at Sep. 30, 2013	$ 1,837,095	$ 1,837,095