CONSOLIDATED STATEMENTS OF CHANGES IN CAPITAL OF ERP OPERATING LIMITED PARTNERSHIP - USD ($) $ in Thousands	Total	ERPOP [Member]	PREFERRED SHARES ERPOP [Member]	General Partner [Member] ERPOP [Member]	Limited Partner ERPOP [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ERPOP [Member]	DISTRIBUTIONS [Member]	PARTIALLY OWNED PROPERTIES [Member] ERPOP [Member]
Balance, beginning of year at Dec. 31, 2017			$ 37,280	$ 10,293,796	$ 226,691	$ (88,612)
Balance, beginning of year at Dec. 31, 2017								$ 4,708
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				4,098	(4,098)
Exercise of EQR share options				30,655
EQR's Employee Share Purchase Plan (ESPP)	$ 3,879
EQR restricted shares				8,258	1
EQR share options				9,734
EQR ESPP discount				767
Net income available to Units - General Partner		$ 654,445		654,445
OP Units - General Partner distributions				(796,212)
Offering costs				(27)
Supplemental Executive Retirement Plan (SERP)				(454)
Change in market value of Redeemable Limited Partners				(13,922)
Adjustment for Limited Partners ownership in Operating Partnership				5,893	(5,893)
Equity compensation associated with Units - Limited Partners					14,009
Net income available to Units - Limited Partners		24,939			24,939
Units - Limited Partners distributions					(28,682)
Change in carrying value of Redeemable Limited Partners					1,771
Unrealized holding gains (losses) arising during the year	2,718	2,718				5,174
Losses reclassified into earnings from other comprehensive income	(18,452)	(18,452)				18,452
Distributions declared per Unit outstanding							$ 2.16
Net income attributable to Noncontrolling Interests	685,192	685,192						2,718
Acquisitions of Noncontrolling Interests – Partially Owned Properties								(13)
Contributions by Noncontrolling Interests								125
Distributions to Noncontrolling Interests								(9,831)
Balance, end of year at Dec. 31, 2018			37,280	10,200,910	228,738	(64,986)
Balance, end of year at Dec. 31, 2018								(2,293)
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				10,410	(10,410)
Exercise of EQR share options				77,785
EQR's Employee Share Purchase Plan (ESPP)	3,116
EQR restricted shares				12,438	2
EQR share options				2,675
EQR ESPP discount				642
Net income available to Units - General Partner		967,287		967,287
OP Units - General Partner distributions				(842,555)
Offering costs				(991)
Supplemental Executive Retirement Plan (SERP)				(1,675)
Change in market value of Redeemable Limited Partners				(82,283)
Adjustment for Limited Partners ownership in Operating Partnership				8,030	(8,030)
Equity compensation associated with Units - Limited Partners					13,410
Net income available to Units - Limited Partners		36,034			36,034
Units - Limited Partners distributions					(29,896)
Change in carrying value of Redeemable Limited Partners					(2,011)
Unrealized holding gains (losses) arising during the year	3,297	3,297				(33,765)
Losses reclassified into earnings from other comprehensive income	(21,188)	(21,188)				21,188
Distributions declared per Unit outstanding							2.27
Net income attributable to Noncontrolling Interests	1,009,708	1,009,708						3,297
Contributions by Noncontrolling Interests								7,337
Distributions to Noncontrolling Interests								(7,158)
Balance, end of year at Dec. 31, 2019			37,280	10,355,789	227,837	(77,563)
Balance, end of year at Dec. 31, 2019								1,183
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				4,696	(4,696)
Exercise of EQR share options				12,275
EQR's Employee Share Purchase Plan (ESPP)	4,508
EQR restricted shares				11,225	13
EQR share options				2,349
EQR ESPP discount				944
Net income available to Units - General Partner		910,546		910,546
OP Units - General Partner distributions				(897,326)
Supplemental Executive Retirement Plan (SERP)				(395)
Change in market value of Redeemable Limited Partners				125,224
Adjustment for Limited Partners ownership in Operating Partnership				2,202	(2,202)
Equity compensation associated with Units - Limited Partners					11,926
Net income available to Units - Limited Partners		34,010			34,010
Units - Limited Partners distributions					(32,951)
Change in carrying value of Redeemable Limited Partners					(775)
Unrealized holding gains (losses) arising during the year	14,855	14,855				(1,190)
Losses reclassified into earnings from other comprehensive income	(35,087)	(35,087)				35,087
Distributions declared per Unit outstanding							$ 2.41
Net income attributable to Noncontrolling Interests	$ 962,501	$ 962,501						14,855
Contributions by Noncontrolling Interests								417
Distributions to Noncontrolling Interests								(11,782)
Balance, end of year at Dec. 31, 2020			$ 37,280	$ 10,532,037	$ 233,162	$ (43,666)
Balance, end of year at Dec. 31, 2020								$ 4,673