Equity, Capital and Other Interests ERP Units (Details)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Capital Unit [Line Items]
Common Shares And Units Outstanding	317,074,506
Issuance of OP Units	3,173,919
Exercise of EQR share options	1,517,880
EQR's Employee Share Purchase Plan (ESPP)	100,222
Restricted Share Grants Net	129,725
Units Issued To Noncontrolling Interests	1,081,797
Units Ownership Interest in Operating Partnership	4.50%
General And Limited Partner [Member]
Capital Unit [Line Items]
Common Shares And Units Outstanding	317,074,506	311,000,728
Issuance of OP Units	3,173,919
Exercise of EQR share options	1,517,880
EQR's Employee Share Purchase Plan (ESPP)	100,222
Restricted Share Grants Net	129,725
Issuance Of LTIPs	70,235
Units Issued To Noncontrolling Interests	1,081,797
Limited Partner [Member]
Capital Unit [Line Items]
Issuance Of LTIPs	70,235
Units Issued To Noncontrolling Interests	1,081,797
Total Units Outstanding	14,399,790	13,492,543
Shares Issued During Period Shares Conversion Of Units To Common Shares	(244,785)
Limited Partner [Member]
Capital Unit [Line Items]
Issuance Of LTIPs	70,235
Units Issued To Noncontrolling Interests	1,081,797
Total Units Outstanding	14,399,790	13,492,543
Shares Issued During Period Shares Conversion Of Units To Common Shares	(244,785)