Consolidated Statements of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Preferred Stock	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	Common Stock	Common Stock	Common Stock Additional Paid- In-Capital
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
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)
DRIP proceeds	99,570		13	99,557
DRIP proceeds (in shares)			1,305,000
Conversion of units of the Operating Partnership to common stock	87,513		11	87,502
Redemption 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 stock		221,965									221,965	201,279	27	201,252
Issuance of stock (shares)													2,640,000
Proceeds from stock options exercised	13,173		4	13,169
Proceeds from stock options exercised (in shares)			383,000
Contributions to consolidated 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)
DRIP proceeds	67			67
Conversion of units of the Operating Partnership to common stock	17,287		2	17,285
Redemption 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 stock	290,699		30	290,669
Issuance of stock (shares)			3,062,000
Proceeds from stock options exercised	12,904		2	12,902
Proceeds from stock options exercised (in shares)			224,000
Contributions-treasury shares	7,120				6,090		1,030
Sale of treasury stock (shares)			83,000
Contributions to consolidated joint venture interest	8,164							8,164
Cash distributions to 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
Balance (in shares) at Dec. 31, 2013			94,993,000
Increase (Decrease) in Stockholders' Equity
Net income	524,646						518,056	6,590
Other comprehensive income:	8,231					8,231
Preferred dividends	(14,952)						(14,952)
DRIP proceeds	64			64
Conversion of units of the Operating Partnership to common stock	31,653		3	31,650
Redemption of units of the Operating Partnership to common stock (in shares)			315,000
Reallocation of noncontrolling interest in the operating partnership	(168,439)						(168,439)
Deferred compensation plan and stock award, net	(1,514)			1,601	(3,115)
Deferred compensation plan and stock award, net (in shares)			15,000
Amortization of deferred compensation plan	29,749			29,749
Issuance of stock	185,321		17	185,304
Issuance of stock (shares)			1,654,000
Proceeds from stock options exercised	25,211		4	25,207
Proceeds from stock options exercised (in shares)			348,000
Contributions to consolidated joint venture interest	30,800							30,800
Cash distributions to noncontrolling interests	(7,019)							(7,019)
Cash distribution declared	(201,411)						(201,411)
Balance at Dec. 31, 2014	$ 7,459,216		$ 1,010	$ 5,289,479	$ (320,471)	$ (6,980)	$ 1,752,404	$ 521,842	$ 0	$ 0	$ 221,932
Balance (in shares) at Dec. 31, 2014			97,325,000