Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended					6 Months Ended				3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Preferred Stock	Jun. 30, 2013 Common Stock	Dec. 31, 2012 Common Stock	Jun. 30, 2013 Accumulated Other Comprehensive Income (Loss)	Jun. 30, 2013 Capital in Excess of Par Value	Jun. 30, 2013 Accumulated Deficit	Jun. 30, 2013 Common Stock Held in Treasury	Jun. 30, 2013 Noncontrolling interests	Jun. 30, 2012 Noncontrolling interests	Jun. 30, 2013 Noncontrolling interests	Jun. 30, 2012 Noncontrolling interests
Increase (Decrease) in Stockholders' Equity
Balance			$ 6,893,089		$ 44,719	$ 31	$ 31	$ (90,900)	$ 9,175,724	$ (3,083,190)	$ (135,781)	$ 977,753	$ 1,215,628	$ 982,486	$ 894,622
Exchange of limited partner units for common shares									5,982			(3,461)	(2,600)	(5,982)	(4,018)
Other			31,998		(165)				(7,499)	(758)	17,750			22,670
Adjustment to limited partners' interest from change in ownership in the Operating Partnership									10,581					(10,581)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests			(834,790)							(715,061)				(119,729)
Distributions to other noncontrolling interest partners			(178)											(178)
Comprehensive income, excluding $957 attributable to preferred interests in the Operating Partnership and $4,532 attributable to noncontrolling redeemable interests in properties in temporary equity			716,128					(11,427)		624,743				102,812
Balance	6,806,247		6,806,247		44,554	31	31	(102,327)	9,184,788	(3,174,266)	(118,031)	971,498	1,185,418	971,498	1,185,418
Comprehensive income attributable to preferred interests					957
Comprehensive income attributable to noncontrolling interests	$ 56,526	$ 33,025	$ 108,302	$ 183,350										$ 4,532