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	233,784	230,585			230,585		3,199
Other comprehensive loss	(1,951)	(1,951)				(1,951)
Issuance of common stock, net	12,277	14,456	555	13,901			(2,179)
Issuance of common stock, net (in shares)			555
Repurchase of common stock	(689)	(689)	(14)	(675)
Repurchase of common stock (in shares)			(14)
Exercise of stock options	20,665	20,665	685	19,980
Exercise of stock options (in shares)			685
Amortization of deferred compensation	5,430	5,430		5,430
Common dividends ($0.545 and $0.525 per share for the period ended March 31, 2014 and 2013, respectively)	(238,467)	(238,467)			(238,467)
Distributions to noncontrolling interests	(3,754)						(3,754)
Issuance of noncontrolling interests	987						987
Balance at Mar. 31, 2013	10,782,059	10,581,266	454,417	11,218,702	(1,075,249)	(16,604)	200,793
Balance (in shares) at Mar. 31, 2013			454,417
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	263,623	259,111			259,111		4,512
Other comprehensive loss	(83)	(83)				(83)
Issuance of common stock, net	32,633	32,706	1,287	31,419			(73)
Issuance of common stock, net (in shares)			1,287
Repurchase of common stock	(8,068)	(8,068)	(208)	(7,860)
Repurchase of common stock (in shares)			(208)
Exercise of stock options	95	95	4	91
Exercise of stock options (in shares)			4
Amortization of deferred compensation	4,890	4,890		4,890
Common dividends ($0.545 and $0.525 per share for the period ended March 31, 2014 and 2013, respectively)	(250,198)	(250,198)			(250,198)
Distributions to noncontrolling interests	(3,975)						(3,975)
Issuance of noncontrolling interests	1,193						1,193
Purchase of noncontrolling interests	(1,671)						(1,671)
Balance at Mar. 31, 2014	$ 10,969,573	$ 10,761,753	$ 458,044	$ 11,362,581	$ (1,044,302)	$ (14,570)	$ 207,820
Balance (in shares) at Mar. 31, 2014			458,044