CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	Total	Total Stockholders' Equity	Preferred Stock	Common Stock	Additional Paid-In Capital	Cumulative Dividends In Excess Of Earnings	Accumulated Other Comprehensive Income (Loss)	Total Noncontrolling Interests
Balance at Dec. 31, 2010	$ 8,146,047	$ 7,957,367	$ 285,173	$ 370,925	$ 8,089,982	$ (775,476)	$ (13,237)	$ 188,680
Balance (in shares) at Dec. 31, 2010			11,820	370,925
Increase (Decrease) in Stockholders' Equity
Net income	308,236	298,852				298,852		9,384
Other comprehensive income (loss)	(596)	(596)					(596)
Issuance of common stock, net	1,269,368	1,271,967		35,691	1,236,276			(2,599)
Issuance of common stock, net (in shares)				35,691
Repurchase of common stock	(4,809)	(4,809)		(131)	(4,678)
Repurchase of common stock (in shares)				(131)
Exercise of stock options	17,016	17,016		635	16,381
Exercise of stock options (in shares)	635			635
Amortization of deferred compensation	10,205	10,205			10,205
Preferred dividends	(10,566)	(10,566)				(10,566)
Common dividends ($1.00 and $0.96 per share for the period ended June 30, 2012 and 2011, respectively)	(374,349)	(374,349)				(374,349)
Distributions to noncontrolling interests	(7,166)							(7,166)
Noncontrolling interest in acquired assets	1,500							1,500
Purchase of noncontrolling interests	(33,618)	(19,559)			(19,559)			(14,059)
Balance at Jun. 30, 2011	9,321,268	9,145,528	285,173	407,120	9,328,607	(861,539)	(13,833)	175,740
Balance (in shares) at Jun. 30, 2011			11,820	407,120
Balance at Dec. 31, 2011	9,220,622	9,033,482	285,173	408,629	9,383,536	(1,024,274)	(19,582)	187,140
Balance (in shares) at Dec. 31, 2011			11,820	408,629
Increase (Decrease) in Stockholders' Equity
Net income	401,539	395,404				395,404		6,135
Other comprehensive income (loss)	(121)	(121)					(121)
Preferred stock redemption	(295,500)	(295,500)	(285,173)			(10,327)
Preferred stock redemption (in shares)			(11,820)
Issuance of common stock, net	753,784	756,057		18,912	737,145			(2,273)
Issuance of common stock, net (in shares)				18,912
Repurchase of common stock	(7,867)	(7,867)		(189)	(7,678)
Repurchase of common stock (in shares)				(189)
Exercise of stock options	37,220	37,220		2,050	35,170
Exercise of stock options (in shares)	2,050			2,050
Amortization of deferred compensation	11,407	11,407			11,407
Preferred dividends	(6,679)	(6,679)				(6,679)
Common dividends ($1.00 and $0.96 per share for the period ended June 30, 2012 and 2011, respectively)	(416,173)	(416,173)				(416,173)
Distributions to noncontrolling interests	(7,778)							(7,778)
Issuance of noncontrolling interests	873							873
Purchase of noncontrolling interests	(388)							(388)
Balance at Jun. 30, 2012	$ 9,690,939	$ 9,507,230		$ 429,402	$ 10,159,580	$ (1,062,049)	$ (19,703)	$ 183,709
Balance (in shares) at Jun. 30, 2012				429,402