Consolidated Statements of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid- In-Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Noncontrolling Interests	Series C Preferred Stock Preferred Stock	Series D Preferred Stock Preferred Stock	Series I Preferred Stock Preferred Stock
Balance at Dec. 31, 2010	$ 5,397,544	$ 817	$ 3,660,842	$ (303,222)	$ (22,659)	$ 1,172,963	$ 518,460	$ 274,022	$ 96,321	$ 0
Balance (in shares) at Dec. 31, 2010		78,307,000
Increase (Decrease) in Stockholders' Equity
Net income	662,493					647,410	15,083
Other comprehensive income:	(5,786)				(5,786)
Preferred dividends	(30,178)					(30,178)
Redemption of units and DRIP proceeds	898		898
Redemption of units and DRIP proceeds (in shares)		13,000
Reallocation of noncontrolling interest in the operating partnership	(39,040)					(39,040)
Deferred compensation plan and stock award, net	(4,787)	3	696	(5,486)
Deferred compensation plan and stock award, net (in shares)		262,000
Amortization of deferred compensation plan	33,252		33,252
Proceeds from issuance of common stock	531,306	70	531,236
Proceeds from issuance of common stock (in shares)		6,957,000
Proceeds from stock options exercised	10,037	2	10,035
Proceeds from stock options exercised (in shares)		244,000
Consolidation of joint venture interest	87,798						87,798
Cash distributions to noncontrolling interests	(143,579)						(143,579)
Cash distribution declared	(46,649)					(46,649)
Balance at Dec. 31, 2011	6,453,309	892	4,236,959	(308,708)	(28,445)	1,704,506	477,762	274,022	96,321	0
Balance (in shares) at Dec. 31, 2011		85,783,000
Increase (Decrease) in Stockholders' Equity
Net income	201,996					196,405	5,591
Other comprehensive income:	(1,142)				(1,142)
Preferred dividends	(30,411)					(30,411)
Redemption of units and DRIP proceeds	99,570	13	99,557
Redemption of units and DRIP proceeds (in shares)		1,305,000
Conversion of units of the Operating Partnership to common stock	87,513	11	87,502
Conversion of units of the Operating Partnership to common stock (in shares)		1,096,000
Redemption of preferred stock	(200,013)					(10,010)		(93,682)	(96,321)
Reallocation of noncontrolling interest in the operating partnership	(61,238)					(61,238)
Deferred compensation plan and stock award, net	(13,428)	3	719	(14,150)
Deferred compensation plan and stock award, net (in shares)		43,000
Amortization of deferred compensation plan	28,742		28,742
Issuance of common stock	221,965									221,965
Proceeds from issuance of common stock	201,279	27	201,252
Proceeds from issuance of common stock (in shares)		2,640,000
Proceeds from stock options exercised	13,173	4	13,169
Proceeds from stock options exercised (in shares)		383,000
Consolidation of joint venture interest	25,894						25,894
Cash distributions to noncontrolling interests	(21,946)						(21,946)
Cash distribution declared	(98,160)					(98,160)
Balance at Dec. 31, 2012	6,907,103	950	4,667,900	(322,858)	(29,587)	1,701,092	487,301	180,340	0	221,965
Balance (in shares) at Dec. 31, 2012		91,250,000
Increase (Decrease) in Stockholders' Equity
Net income	146,000					135,371	10,629
Other comprehensive income:	14,376				14,376
Preferred dividends	(21,881)					(21,881)
Redemption of units and DRIP proceeds	67		67
Conversion of units of the Operating Partnership to common stock	17,287	2	17,285
Conversion of units of the Operating Partnership to common stock (in shares)		239,000
Redemption of preferred stock	(192,500)					(12,160)		(180,340)
Preferred stock issuance costs	(33)									(33)
Reallocation of noncontrolling interest in the operating partnership	(45,618)					(45,618)
Deferred compensation plan and stock award, net	166	2	752	(588)
Deferred compensation plan and stock award, net (in shares)		135,000
Amortization of deferred compensation plan	26,329		26,329
Issuance of common stock	290,699	30	290,669
Issuance of common stock (shares)		3,062,000
Proceeds from issuance of common stock	12,904	2	12,902
Proceeds from issuance of common stock (in shares)		224,000
Sale of treasury stock	7,120			6,090		1,030
Sale of treasury stock (shares)		83,000
Contribution to consolidated joint venture interest	8,164						8,164
Cash contributions from noncontrolling interests	(14,623)						(14,623)
Cash distribution declared	(138,684)					(138,684)
Balance at Dec. 31, 2013	$ 7,016,876	$ 986	$ 5,015,904	$ (317,356)	$ (15,211)	$ 1,619,150	$ 491,471	$ 0	$ 0	$ 221,932