CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total Stockholders' Equity	Common Stock	Additional Paid-In Capital	Cumulative Dividends In Excess Of Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Total
Balance at Dec. 31, 2012	$ 10,551,237	$ 453,191	$ 11,180,066	$ (1,067,367)	$ (14,653)	$ 202,540	$ 10,753,777
Balance (in shares) at Dec. 31, 2012		453,191
Increase (Decrease) in Stockholders' Equity
Net (loss) income	970,837			970,837		14,169	985,006
Other comprehensive income	166				166		166
Issuance of common stock, net	110,701	$ 3,136	107,565			(3,683)	107,018
Issuance of common stock, net (in shares)		3,136
Repurchase of common stock	(10,438)	$ (242)	(10,196)				(10,438)
Repurchase of common stock (in shares)		(242)
Exercise of stock options	17,502	$ 876	16,626				17,502
Exercise of stock options (in shares)		876
Amortization of deferred compensation	39,980		39,980				39,980
Common dividends ($2.26, $2.18 and $2.10 per share for the year ended 2015, 2014 and 2013, respectively)	(956,685)			(956,685)			(956,685)
Distributions to noncontrolling interests						(17,664)	(17,664)
Issuance of noncontrolling interests						12,472	12,472
Balance at Dec. 31, 2013	10,723,300	$ 456,961	11,334,041	(1,053,215)	(14,487)	207,834	10,931,134
Balance (in shares) at Dec. 31, 2013		456,961
Increase (Decrease) in Stockholders' Equity
Net (loss) income	922,233			922,233		14,358	936,591
Other comprehensive income	(9,408)				(9,408)		(9,408)
Issuance of common stock, net	92,688	$ 2,939	89,749			(557)	92,131
Issuance of common stock, net (in shares)		2,939
Repurchase of common stock	(12,703)	$ (323)	(12,380)				(12,703)
Repurchase of common stock (in shares)		(323)
Exercise of stock options	4,461	$ 169	4,292				4,461
Exercise of stock options (in shares)		169
Amortization of deferred compensation	21,885		21,885				21,885
Common dividends ($2.26, $2.18 and $2.10 per share for the year ended 2015, 2014 and 2013, respectively)	(1,001,559)			(1,001,559)			(1,001,559)
Distributions to noncontrolling interests						(15,611)	(15,611)
Issuance of noncontrolling interests						57,746	57,746
Purchase of noncontrolling interests	(5,600)		(5,600)			(1,968)	(7,568)
Balance at Dec. 31, 2014	10,735,297	$ 459,746	11,431,987	(1,132,541)	(23,895)	261,802	10,997,099
Balance (in shares) at Dec. 31, 2014		459,746
Increase (Decrease) in Stockholders' Equity
Net (loss) income	(559,235)			(559,235)		12,817	(546,418)
Other comprehensive income	(6,575)				(6,575)		(6,575)
Issuance of common stock, net	182,067	$ 5,117	176,950			(3,183)	$ 178,884
Issuance of common stock, net (in shares)		5,117					1,800
Repurchase of common stock	(8,738)	$ (198)	(8,540)				$ (8,738)
Repurchase of common stock (in shares)		(198)
Exercise of stock options	27,587	$ 823	26,764				27,587
Exercise of stock options (in shares)		823
Amortization of deferred compensation	26,127		26,127				26,127
Common dividends ($2.26, $2.18 and $2.10 per share for the year ended 2015, 2014 and 2013, respectively)	(1,046,638)			(1,046,638)			(1,046,638)
Distributions to noncontrolling interests	(263)		(263)			(18,884)	(19,147)
Issuance of noncontrolling interests						151,185	151,185
Purchase of noncontrolling interests	(5,986)		(5,986)			(1,063)	(7,049)
Balance at Dec. 31, 2015	$ 9,343,643	$ 465,488	$ 11,647,039	$ (2,738,414)	$ (30,470)	$ 402,674	$ 9,746,317
Balance (in shares) at Dec. 31, 2015		465,488