Equity (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended					3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Preferred Stock	Mar. 31, 2014 Common Stock	Dec. 31, 2013 Common Stock	Mar. 31, 2014 Accumulated Other Comprehensive Income (Loss)	Mar. 31, 2014 Capital in Excess of Par Value	Mar. 31, 2014 Accumulated Deficit	Mar. 31, 2014 Common Stock Held in Treasury	Mar. 31, 2014 Noncontrolling Interests	Mar. 31, 2013 Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity
Balance	$ 6,822,632		$ 44,390	$ 31	$ 31	$ (75,795)	$ 9,217,363	$ (3,218,686)	$ (117,897)	$ 973,226	$ 982,486
Exchange of limited partner units for common shares							911			(911)	(2,521)
Issuance of limited partner units	84,910									84,910
Contributions from noncontrolling interest partners and other	7,634		(82)				2,821	(7,791)	201	12,485
Purchase and dispositions of noncontrolling interests, net	6,130									6,130
Adjustment to limited partners' interest from change in ownership in the Operating Partnership							67,226			(67,226)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(454,802)							(389,097)		(65,705)
Distributions to other noncontrolling interest partners	(11,731)									(11,731)
Comprehensive income, excluding $479 attributable to preferred interests in the Operating Partnership and $492 attributable to noncontrolling redeemable interests in properties in temporary equity	409,508					8,216		342,482		58,810
Comprehensive income attributable to preferred interests in the Operating Partnership			(479)
Balance	6,864,281		44,308	31	31	(67,579)	9,288,321	(3,273,092)	(117,696)	989,988	977,753
Comprehensive income attributable to noncontrolling redeemable interests in properties in temporary equity	$ 59,782	$ 51,776								$ 492