Equity, Capital and Other Interests - Changes in Operating Partnership's Issued and Outstanding Units (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
General and Limited Partner Units
Common Shares And Units Outstanding	380,496,999	379,182,608
Exercise of share options	846,137	815,044	1,456,363
Employee Share Purchase Plan (ESPP)	68,286	63,909	68,462
Restricted share grants, net	83,451	147,689	168,142
Restricted unit grants, net	291,647	287,749	335,496
Common Shares And Units Outstanding	381,786,520	380,496,999	379,182,608
LIMITED PARTNERS
Total Units Outstanding	14,626,075	14,427,164	14,298,691
Restricted unit grants, net	291,647	287,749	335,496
Conversion of restricted shares to restricted units	0	0	1,284
Conversion of Limited Partner OP Units to EQR Common Shares	(1,149,284)	(88,838)	(208,307)
Total Units Outstanding	13,768,438	14,626,075	14,427,164
Units Ownership Interest in Operating Partnership	3.60%	3.80%	3.80%
ERPOP [Member]
General and Limited Partner Units
Common Shares And Units Outstanding	380,496,999	379,182,608	377,154,145
Exercise of share options	846,137	815,044	1,456,363
Employee Share Purchase Plan (ESPP)	68,286	63,909	68,462
Restricted share grants, net	83,451	147,689	168,142
Restricted unit grants, net	291,647	287,749	335,496
Common Shares And Units Outstanding	381,786,520	380,496,999	379,182,608
LIMITED PARTNERS
Total Units Outstanding	14,626,075	14,427,164	14,298,691
Restricted unit grants, net	291,647	287,749	335,496
Conversion of restricted shares to restricted units	0	0	1,284
Conversion of Limited Partner OP Units to EQR Common Shares	(1,149,284)	(88,838)	(208,307)
Total Units Outstanding	13,768,438	14,626,075	14,427,164
Units Ownership Interest in Operating Partnership	3.60%	3.80%	3.80%