Equity, Capital and Other Interests EQR Common Shares (Details)	9 Months Ended		9 Months Ended			12 Months Ended	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Archstone Transaction [Member]	Sep. 30, 2013 Limited Partner [Member]	Dec. 31, 2012 Limited Partner [Member]	Dec. 31, 2012 Public Offering [Member]	Sep. 30, 2013 Limited Partner [Member]	Dec. 31, 2012 Limited Partner [Member]
Common Shares outstanding at January 1,	360,395,959	325,054,654
Common Shares Issued:
Conversion of OP Units	47,939
Issuance of Common Shares	34,468,085		34,468,085			21,850,000
Exercise of share options	530,847
Employee Share Purchase Plan (ESPP)	63,788
Restricted Share Grants Net	230,646
Units
Total Units Outstanding				14,200,376	13,968,758		14,200,376	13,968,758
Issuance Of LTIPs				279,557			279,557
Shares Issued During Period Shares Conversion Of Units To Common Shares				(47,939)			(47,939)
Common Shares And Units Outstanding	374,596,335
Units Ownership Interest in Operating Partnership	3.80%