Equity, Capital and other Interests (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2011
Common Shares
Common Shares outstanding at January 1,	290,197,242
Common Shares Issued:
Conversion of OP Units	324,649
Issuance of Common Shares	3,038,980
Exercise of share options	2,914,476
Employee Share Purchase Plan (ESPP)	98,766
Restricted share grants, net	148,708
Common Shares Other:
Conversion of restricted shares to LTIP Units	(101,988)
Common Shares outstanding at September 30,	296,620,833
Units
Units outstanding at January 1,	13,612,037
LTIP Units, net	120,112
Conversion of restricted shares to LTIP Units	101,988
Conversion of OP Units to Common Shares	(324,649)
Units outstanding at September 30,	310,130,321
Units Ownership Interest in Operating Partnership	4.40%
EQR restricted share grants, net	148,708
Redeemable noncontrolling interests rollforward
Balance at January 1	$ 383,540
Change in market value	(16,023)
Change in carrying value	11,281
Balance at September 30,	378,798
OPERATING PARTNERSHIP
Redeemable noncontrolling interests rollforward
Change in carrying value	11,281
Balance at September 30,	378,800
OPERATING PARTNERSHIP \| General And Limited Partner [Member]
Common Shares
Common Shares outstanding at January 1,	303,809,279
Units
Total Common Shares and Units outstanding at September 30,	310,130,321
OPERATING PARTNERSHIP \| GENERAL PARTNER
Common Shares Issued:
Issuance of Common Shares	3,038,980
Restricted share grants, net	148,708
Units
LTIP Units, net	120,112
Exercise of EQR share options	2,914,476
Employee Share Purchase Plan (ESPP)	98,766
EQR restricted share grants, net	148,708
OPERATING PARTNERSHIP \| LIMITED PARTNERS
Units
Units outstanding at January 1,	13,612,037
LTIP Units, net	120,112
Conversion of restricted shares to LTIP Units	101,988
Conversion of OP Units to Common Shares	(324,649)
Units outstanding at September 30,	13,509,488
Units Ownership Interest in Operating Partnership	4.40%
Redeemable noncontrolling interests rollforward
Balance at January 1	383,540
Change in market value	(16,023)
Change in carrying value	11,281
Balance at September 30,	$ 378,798

Number of all classes of common stock held by shareholders, which is net of related treasury stock, and number of all Operating Partnership Units held by various individuals and entities that contributed their properties to the Operating Partnership.

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Common Shares Other.

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Number of all Operating Partnership Units held by various individuals and entities that contributed their properties to the Operating Partnership. These units are referred to as noncontrolling interests.

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