Capital and Redeemable Limited Partners of ERP Operating Limited Partnership - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Common Shares And Units Outstanding	379,182,608	377,154,145	374,659,636
Exercise of EQR share options	1,456,363	2,086,380	586,017
EQR's Employee Share Purchase Plan (ESPP)	68,462	68,807	73,468
EQR's restricted share grants, net	168,142	169,722	229,097
Stock Repurchased and Retired During Period, Shares	0	(31,240)	0
Conversion of restricted shares to restricted units	(1,284)	(12,146)	0
Units Ownership Interest in Operating Partnership	3.80%	3.80%	3.80%
ERPOP [Member]
Restricted unit grants, net	335,496	200,840	279,557
Stock Repurchased and Retired During Period, Shares		(31,240)
Conversion of restricted shares to restricted units	1,284	12,146	0
Shares Issued During Period Shares Conversion Of Units To Common Shares	(208,307)	(94,671)	(67,939)
Total Units Outstanding	14,427,164	14,298,691	14,180,376	13,968,758
Redeemable Limited Partners	$ 566,783	$ 500,733	$ 363,144	$ 398,372
Limited Partners Change In Redemption Value	64,378	139,818	(79,667)
Limited Partners Change In Carrying Value	$ 1,672	$ (2,229)	$ 44,439
ERPOP [Member] | General And Limited Partner [Member]
Common Shares And Units Outstanding	379,182,608	377,154,145	374,659,636	339,023,412
Issuance of OP Units	0	0	34,468,085
Exercise of EQR share options	1,456,363	2,086,380	586,017
EQR's Employee Share Purchase Plan (ESPP)	68,462	68,807	73,468
EQR's restricted share grants, net	168,142	169,722	229,097
Restricted unit grants, net	335,496	200,840	279,557
Stock Repurchased and Retired During Period, Shares	0	(31,240)	0
ERPOP [Member] | ERPOP [Member]
Restricted unit grants, net	335,496	200,840	279,557
Conversion of restricted shares to restricted units	1,284	12,146	0
Shares Issued During Period Shares Conversion Of Units To Common Shares	(208,307)	(94,671)	(67,939)
Total Units Outstanding	14,427,164	14,298,691	14,180,376	13,968,758
Units Ownership Interest in Operating Partnership	3.80%	3.80%	3.80%