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, 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 ($1.05 and $1.00 per share for the period ended June 30, 2013 and 2012, 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
Balance at Dec. 31, 2012	10,753,777	10,551,237		453,191	11,180,066	(1,067,367)	(14,653)	202,540
Balance (in shares) at Dec. 31, 2012				453,191
Increase (Decrease) in Stockholders' Equity
Net income	450,509	443,986				443,986		6,523
Other comprehensive income (loss)	2,293	2,293					2,293
Issuance of common stock, net	47,321	50,318		1,097	49,221			(2,997)
Issuance of common stock, net (in shares)				1,097
Repurchase of common stock	(2,270)	(2,270)		(46)	(2,224)
Repurchase of common stock (in shares)				(46)
Exercise of stock options	16,809	16,809		852	15,957
Exercise of stock options (in shares)	852			852
Amortization of deferred compensation	11,638	11,638			11,638
Common dividends ($1.05 and $1.00 per share for the period ended June 30, 2013 and 2012, respectively)	(477,453)	(477,453)				(477,453)
Distributions to noncontrolling interests	(7,506)							(7,506)
Issuance of noncontrolling interests	3,141							3,141
Balance at Jun. 30, 2013	$ 10,798,259	$ 10,596,558		$ 455,094	$ 11,254,658	$ (1,100,834)	$ (12,360)	$ 201,701
Balance (in shares) at Jun. 30, 2013				455,094