Equity, Capital and Other Interests EQR Common Shares (Details)	3 Months Ended		3 Months Ended			12 Months Ended	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Archstone Transaction [Member]	Mar. 31, 2013 Limited Partner [Member]	Dec. 31, 2012 Limited Partner [Member]	Dec. 31, 2012 Public Offering [Member]	Mar. 31, 2013 Limited Partner [Member]	Dec. 31, 2012 Limited Partner [Member]
Common Shares outstanding at January 1,	360,063,675	325,054,654
Common Shares Issued:
Conversion of OP Units	23,964
Issuance of Common Shares	34,468,085		34,468,085			21,850,000
Exercise of share options	268,547
Employee Share Purchase Plan (ESPP)	37,704
Restricted Share Grants Net	210,721
Units
Total Units Outstanding				14,226,725	13,968,758		14,226,725	13,968,758
Issuance Of LTIPs				281,931			281,931
Shares Issued During Period Shares Conversion Of Units To Common Shares				(23,964)			(23,964)
Common Shares And Units Outstanding	374,290,400
Units Ownership Interest in Operating Partnership	3.80%