Consolidated Statements of Equity (USD $) In Thousands, unless otherwise specified	Total	Preferred Stock	Preferred Stock Series J Preferred stock	Common Stock	Accumulated Other Comprehensive Income (Loss)	Capital in Excess of Par Value	Accumulated Deficit	Common Stock Held in Treasury	Noncontrolling Interests
Balance at Dec. 31, 2010	$ 5,633,752	$ 45,375		$ 30	$ 6,530	$ 8,059,852	$ (3,114,571)	$ (166,436)	$ 802,972
Increase (Decrease) in Stockholders' Equity
Exchange of limited partner units (596,051 common shares in 2013, 7,447,921 units for 6,795,296 common shares in 2012 and 584,432 common shares in 2011, Note 10)						9,465			(9,465)
Issuance of limited partner units	9,084								9,084
Stock options exercised (common shares: 1,567 in 2013, 712 in 2012 and 324,720 in 2011, respectively and net of 76,969 shares used to fund required withholding tax in 2011)	2,095					2,095
Common Stock Retired (61,584 common shares)	(6,385)					(6,385)
Series J preferred stock premium amortization	(328)		(328)
Stock incentive program (common shares, net: 107,123 in 2013, 114,066 in 2012 and 116,885 in 2011)						(13,000)		13,000
Amortization of stock incentive	14,018					14,018
Issuance of unit equivalents and other	21,940					1,056	(131,224)	895	151,213
Adjustment to limited partners' interest from change in ownership in the Operating Partnership						36,032			(36,032)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(1,242,241)						(1,030,744)		(211,497)
Distribution to other noncontrolling interest partners	(1,029)								(1,029)
Other comprehensive income	(121,657)				(100,793)				(20,864)
Net income, excluding $1,915, $1,915 and $1,915 attributable to preferred interests in the Operating Partnership during 2013, 2012 and 2011, respectively and $8,858, $8,520 and $8,946 attributable to noncontrolling redeemable interests in properties in temporary equity during 2013, 2012 and 2011, respectively	1,235,039						1,024,799		210,240
Balance at Dec. 31, 2011	5,544,288	45,047		30	(94,263)	8,103,133	(3,251,740)	(152,541)	894,622
Increase (Decrease) in Stockholders' Equity
Exchange of limited partner units (596,051 common shares in 2013, 7,447,921 units for 6,795,296 common shares in 2012 and 584,432 common shares in 2011, Note 10)						144,197			(144,197)
Public offering of common stock (9,137,500 common shares)	1,213,741			1		1,213,740
Issuance of limited partner units	31,324								31,324
Stock options exercised (common shares: 1,567 in 2013, 712 in 2012 and 324,720 in 2011, respectively and net of 76,969 shares used to fund required withholding tax in 2011)	41					41
Redemption of limited partner units	(248,000)					(209,096)			(38,904)
Series J preferred stock premium amortization	(328)		(328)
Stock incentive program (common shares, net: 107,123 in 2013, 114,066 in 2012 and 116,885 in 2011)						(16,760)		16,760
Amortization of stock incentive	14,001					14,001
Purchase of noncontrolling interests	84,476					25,917			58,559
Other	20,463					385	(21,393)		41,471
Adjustment to limited partners' interest from change in ownership in the Operating Partnership						(99,834)			99,834
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(1,483,325)						(1,244,553)		(238,772)
Distribution to other noncontrolling interest partners	(435)								(435)
Other comprehensive income	7,646				3,363				4,283
Net income, excluding $1,915, $1,915 and $1,915 attributable to preferred interests in the Operating Partnership during 2013, 2012 and 2011, respectively and $8,858, $8,520 and $8,946 attributable to noncontrolling redeemable interests in properties in temporary equity during 2013, 2012 and 2011, respectively	1,709,197						1,434,496		274,701
Balance at Dec. 31, 2012	6,893,089	44,719		31	(90,900)	9,175,724	(3,083,190)	(135,781)	982,486
Increase (Decrease) in Stockholders' Equity
Exchange of limited partner units (596,051 common shares in 2013, 7,447,921 units for 6,795,296 common shares in 2012 and 584,432 common shares in 2011, Note 10)						11,161			(11,161)
Stock options exercised (common shares: 1,567 in 2013, 712 in 2012 and 324,720 in 2011, respectively and net of 76,969 shares used to fund required withholding tax in 2011)	90					90
Series J preferred stock premium amortization	(329)		(329)
Stock incentive program (common shares, net: 107,123 in 2013, 114,066 in 2012 and 116,885 in 2011)						(17,884)		17,884
Amortization of stock incentive	18,311					18,311
Issuance of unit equivalents and other	41,885					346	(9,095)		50,634
Adjustment to limited partners' interest from change in ownership in the Operating Partnership						29,615			(29,615)
Distributions to common stockholders and limited partners, excluding Operating Partnership preferred interests	(1,688,638)						(1,446,042)		(242,596)
Distribution to other noncontrolling interest partners	(285)								(285)
Other comprehensive income	17,692				15,105				2,587
Net income, excluding $1,915, $1,915 and $1,915 attributable to preferred interests in the Operating Partnership during 2013, 2012 and 2011, respectively and $8,858, $8,520 and $8,946 attributable to noncontrolling redeemable interests in properties in temporary equity during 2013, 2012 and 2011, respectively	1,540,817						1,319,641		221,176
Balance at Dec. 31, 2013	$ 6,822,632	$ 44,390		$ 31	$ (75,795)	$ 9,217,363	$ (3,218,686)	$ (117,897)	$ 973,226