Equity, Capital and Other Interests EQR Common Shares (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Stock, Shares, Outstanding January 1,	362,855,454	360,479,260	325,054,654	297,508,185
Common Shares Issued:
Conversion of OP Units	94,671	67,939	675,817
Stock Issued During Period, Shares, New Issues	0	34,468,085	25,023,919
Exercise of share options	2,086,380	586,017	1,608,427
Employee Share Purchase Plan (ESPP)	68,807	73,468	110,054
Restricted Share Grants Net	169,722	229,097	128,252
Common Shares Other:
Conversion of restricted shares to restricted units	(12,146)	0	0
Stock Repurchased and Retired During Period, Shares	(31,240)	0	0
Units
Common Shares And Units Outstanding	377,154,145	374,659,636	339,023,412
Units Ownership Interest in Operating Partnership	3.80%	3.80%	4.10%
OP Units Issued:
Issue Price Per OP Unit			$ 61.57
Valuation Operating Partnership Unit			$ 66,600,000
Limited Partner [Member]
Common Shares Other:
Conversion of restricted shares to restricted units	12,146	0	0
Units
Total Units Outstanding	14,298,691	14,180,376	13,968,758	13,492,543
Issuance Of Restricted Units	200,840	279,557	70,235
Issuance Of Units	0	0	1,081,797
Shares Issued During Period Shares Conversion Of Units To Common Shares	(94,671)	(67,939)	(675,817)
OP Units Issued:
Valuation Operating Partnership Unit			$ 66,600,000