Equity (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended					9 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Preferred Stock	Sep. 30, 2013 Common Stock	Dec. 31, 2012 Common Stock	Sep. 30, 2013 Accumulated Other Comprehensive Income (Loss)	Sep. 30, 2013 Capital in Excess of Par Value	Sep. 30, 2013 Accumulated Deficit	Sep. 30, 2013 Common Stock Held in Treasury	Sep. 30, 2013 Noncontrolling interests	Sep. 30, 2012 Noncontrolling interests	Sep. 30, 2013 Noncontrolling interests	Sep. 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)	$ 971,498	$ 1,185,418	$ 982,486	$ 894,622
Exchange of limited partner units for common shares									6,041			(59)	(129,783)	(6,041)	(133,801)
Contributions from noncontrolling interest partners and other			53,384		(247)				(3,248)	(170)	17,750			39,299
Adjustment to limited partners' interest from change in ownership in the Operating Partnership									19,422					(19,422)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests			(1,252,637)							(1,072,782)				(179,855)
Distributions to other noncontrolling interest partners			(249)											(249)
Comprehensive income, excluding $1,436 attributable to preferred interests in the Operating Partnership and $6,499 attributable to noncontrolling redeemable interests in properties in temporary equity			1,110,906					14,198		937,252				159,456
Balance	6,804,493		6,804,493		44,472	31	31	(76,702)	9,197,939	(3,218,890)	(118,031)	975,674	979,364	975,674	979,364
Comprehensive income attributable to preferred interests					1,436
Comprehensive income attributable to noncontrolling interests	$ 59,089	$ 56,077	$ 167,391	$ 239,427										$ 6,499