CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Thousands, unless otherwise specified	Total	Total Stockholders' Equity	Common Stock	Additional Paid-In Capital	Cumulative Dividends In Excess Of Earnings	Accumulated Other Comprehensive Income (Loss)	Total Noncontrolling Interests
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	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
Amortization of deferred compensation	11,638	11,638		11,638
Common dividends ($1.09 and $1.05 per share for the period ended June 30, 2014 and 2013, 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
Balance at Dec. 31, 2013	10,931,134	10,723,300	456,961	11,334,041	(1,053,215)	(14,487)	207,834
Balance (in shares) at Dec. 31, 2013			456,961
Increase (Decrease) in Stockholders' Equity
Net income	485,902	477,996			477,996		7,906
Other comprehensive income	2,818	2,818				2,818
Issuance of common stock, net	53,609	53,682	1,954	51,728			(73)
Issuance of common stock, net (in shares)			1,954
Repurchase of common stock	(11,086)	(11,086)	(284)	(10,802)
Repurchase of common stock (in shares)			(284)
Exercise of stock options	2,792	2,792	111	2,681
Exercise of stock options (in shares)			111
Amortization of deferred compensation	11,006	11,006		11,006
Common dividends ($1.09 and $1.05 per share for the period ended June 30, 2014 and 2013, respectively)	(500,364)	(500,364)			(500,364)
Distributions to noncontrolling interests	(7,967)						(7,967)
Issuance of noncontrolling interests	6,434						6,434
Purchase of noncontrolling interests	(1,684)	(13)		(13)			(1,671)
Balance at Jun. 30, 2014	$ 10,972,594	$ 10,760,131	$ 458,742	$ 11,388,641	$ (1,075,583)	$ (11,669)	$ 212,463
Balance (in shares) at Jun. 30, 2014			458,742