Equity (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Increase (Decrease) in Stockholders' Equity
Balance			$ 5,951,505
Redemption of limited partner units			(162,684)
Treasury stock purchase			(343,007)
LTIP units			23,640
Purchase and dispositions of noncontrolling interests, net and other			3,278
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests			(1,054,133)
Distributions to other noncontrolling interest partners			(2,080)
Comprehensive income, excluding $958 attributable to preferred interests in the Operating Partnership			762,630
Balance	$ 5,179,149		5,179,149
Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance			44,062
Purchase and dispositions of noncontrolling interests, net and other			(164)
Balance	43,898		43,898
Preferred Stock | Operating Partnership
Increase (Decrease) in Stockholders' Equity
Comprehensive income attributable to preferred interests			958
Common Stock.
Increase (Decrease) in Stockholders' Equity
Balance			31
Balance	31		31
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity
Balance			(61,041)
Comprehensive income, excluding $958 attributable to preferred interests in the Operating Partnership			(185,534)
Balance	(246,575)		(246,575)
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity
Balance			9,422,237
Exchange of limited partner units for common shares			7,905
Redemption of limited partner units			(147,841)
Purchase and dispositions of noncontrolling interests, net and other			(6,263)
Adjustment to limited partners' interest from change in ownership in the Operating Partnership			81,529
Balance	9,357,567		9,357,567
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance			(4,208,183)
Purchase and dispositions of noncontrolling interests, net and other			(78)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests			(902,815)
Comprehensive income, excluding $958 attributable to preferred interests in the Operating Partnership			836,787
Balance	(4,274,289)		(4,274,289)
Common Stock Held in Treasury
Increase (Decrease) in Stockholders' Equity
Balance			(103,929)
Treasury stock purchase			(343,007)
Purchase and dispositions of noncontrolling interests, net and other			9,185
Balance	(437,751)		(437,751)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity
Balance	828,618	$ 989,988	858,328	$ 973,226
Exchange of limited partner units for common shares	(56)	(279)	(7,905)	(1,190)
Redemption of limited partner units			(14,843)
LTIP units			23,640
Purchase and dispositions of noncontrolling interests, net and other	415	4,599	598	10,729
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(75,905)	(121,454)	(81,529)	(188,680)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests			(151,318)
Distributions to other noncontrolling interest partners			(2,080)
Comprehensive income, excluding $958 attributable to preferred interests in the Operating Partnership			111,377
Balance	$ 736,268	$ 882,344	$ 736,268	$ 882,344