Equity (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity
Balance	$ 5,951,505
LTIP units	11,828
Purchase and dispositions of noncontrolling interests, net and other	(5,629)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(510,149)
Distributions to other noncontrolling interest partners	(1,372)
Comprehensive income, excluding $479 attributable to preferred interests in the Operating Partnership	318,880
Balance	5,765,063
Preferred Stock
Increase (Decrease) in Stockholders' Equity
Balance	44,062
Purchase and dispositions of noncontrolling interests, net and other	(82)
Balance	43,980
Comprehensive income attributable to preferred interests	479
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 $479 attributable to preferred interests in the Operating Partnership	(90,790)
Balance	(151,831)
Capital in Excess of Par Value
Increase (Decrease) in Stockholders' Equity
Balance	9,422,237
Exchange of limited partner units for common shares	7,849
Purchase and dispositions of noncontrolling interests, net and other	1,628
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	5,624
Balance	9,437,338
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity
Balance	(4,208,183)
Purchase and dispositions of noncontrolling interests, net and other	(7,313)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(436,611)
Comprehensive income, excluding $479 attributable to preferred interests in the Operating Partnership	363,008
Balance	(4,289,099)
Common Stock Held in Treasury
Increase (Decrease) in Stockholders' Equity
Balance	(103,929)
Purchase and dispositions of noncontrolling interests, net and other	(45)
Balance	(103,974)
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity
Balance	858,328	973,226
Exchange of limited partner units for common shares	(7,849)	(911)
LTIP units	11,828
Purchase and dispositions of noncontrolling interests, net and other	183	6,130
Adjustment to limited partners' interest from change in ownership in the Operating Partnership	(5,624)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(73,538)
Distributions to other noncontrolling interest partners	(1,372)
Comprehensive income, excluding $479 attributable to preferred interests in the Operating Partnership	46,662
Balance	$ 828,618	$ 989,988