Equity, Capital and Other Interests EQR Common Shares (Details) - shares	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Common Shares of beneficial interest, shares outstanding	364,140,040	362,855,454
Common Shares Issued:
Conversion of OP Units	181,753
Exercise of share options	882,764
Employee Share Purchase Plan (ESPP)	52,869
Restricted share grants, net	168,484
Conversion of restricted shares to restricted units	(1,284)
Units
Common Shares And Units Outstanding	378,595,767
Units Ownership Interest in Operating Partnership	3.80%
ERPOP [Member]
Limited Partners' Capital Account, Units Outstanding	14,455,727	14,298,691
Common Shares Issued:
Conversion of OP Units	(181,753)
Exercise of share options	882,764
Employee Share Purchase Plan (ESPP)	52,869
Restricted share grants, net	168,484
Conversion of restricted shares to restricted units	1,284
Units
Restricted units, net	337,505
Common Shares And Units Outstanding	378,595,767	377,154,145
Units Ownership Interest in Operating Partnership	3.80%