Equity, Capital and other Interests (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2011
Common Shares
Common Shares outstanding at January 1,	290,197,242
Common Shares Issued:
Conversion of OP Units	284,691
Issuance of Common Shares	3,038,980
Exercise of share options	2,632,021
Employee Share Purchase Plan (ESPP)	78,121
Restricted share grants, net	151,018
Conversion of restricted shares to LTIP Units	(101,988)
Common Shares Other:
Common Shares outstanding at June 30,	296,280,085
Units
Units outstanding at January 1,	13,612,037
Issuance of LTIP Units Net	58,942
Conversion of restricted shares to LTIP Units	101,988
Conversion of OP Units to Common Shares	(284,691)
Units outstanding at June 30,	13,488,276
Total Common Shares and Units outstanding at June 30,	309,768,361
Units Ownership Interest in Operating Partnership	4.40%
EQR restricted share grants, net	151,018
Redeemable noncontrolling interests rollforward
Balance at January 1	$ 383,540
Change in market value	41,377
Change in carrying value	13,224
Balance at June 30	438,141
OPERATING PARTNERSHIP
Redeemable noncontrolling interests rollforward
Change in carrying value	13,224
Balance at June 30,	416,334
OPERATING PARTNERSHIP | GENERAL PARTNER
Common Shares Issued:
Issuance of Common Shares	3,038,980
Restricted share grants, net	151,018
Units
Issuance of LTIP Units Net	58,942
Exercise of EQR share options	2,632,021
Employee Share Purchase Plan (ESPP)	78,121
EQR restricted share grants, net	151,018
OPERATING PARTNERSHIP | LIMITED PARTNERS
Units
Units outstanding at January 1,	13,612,037
Issuance of LTIP Units Net	58,942
Conversion of restricted shares to LTIP Units	101,988
Conversion of OP Units to Common Shares	(284,691)
Units outstanding at June 30,	13,488,276
Units Ownership Interest in Operating Partnership	4.40%
Redeemable noncontrolling interests rollforward
Balance at January 1	383,540
Change in market value	41,377
Change in carrying value	13,224
Balance at June 30,	$ 438,141
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 June 30,	309,768,361