CONSOLIDATED STATEMENTS OF CHANGES IN CAPITAL OF ERP OPERATING LIMITED PARTNERSHIP (Unaudited) - 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, 2019			$ 37,280	$ 10,355,789	$ 227,837	$ (77,563)
Balance, beginning of year at Dec. 31, 2019								$ 1,183
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				3,856	(3,856)
Exercise of EQR share options				11,322
EQR's Employee Share Purchase Plan (ESPP)				2,359
EQR restricted shares				7,254	12
EQR share options				1,293
EQR ESPP discount				416
Net income available to Units - General Partner		$ 567,949		567,949
OP Units General Partner distributions				(448,750)
Supplemental Executive Retirement Plan (SERP)				(506)
Change in market value of Redeemable Limited Partners				128,753
Adjustment for Limited Partners ownership in Operating Partnership				(1,987)	1,987
Equity compensation associated with Units - Limited Partners					7,026
Net income available to Units - Limited Partners		21,248			21,248
Units - Limited Partners distributions					(17,037)
Change in carrying value of Redeemable Limited Partners					(2,048)
Unrealized holding (losses) arising during the period	$ 13,410	13,410				(1,190)
Losses reclassified into earnings from other comprehensive income	(11,398)	(11,398)				11,398
Distributions declared per Unit outstanding							$ 1.205
Net income attributable to Noncontrolling Interests	604,152	604,152						13,410
Contributions by Noncontrolling Interests								341
Distributions to Noncontrolling Interests								(10,300)
Balance, end of period at Jun. 30, 2020			37,280	10,627,748	235,169	(67,355)
Balance, end of period at Jun. 30, 2020								4,634
Balance, beginning of year at Mar. 31, 2020			37,280	10,565,983	235,580	(72,896)
Balance, beginning of year at Mar. 31, 2020								4,739
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				2,012	(2,012)
Exercise of EQR share options				171
EQR's Employee Share Purchase Plan (ESPP)				1,490
EQR restricted shares				3,231
EQR share options				623
EQR ESPP discount				263
Net income available to Units - General Partner		260,116		260,116
OP Units General Partner distributions				(224,243)
Supplemental Executive Retirement Plan (SERP)				(655)
Change in market value of Redeemable Limited Partners				17,304
Adjustment for Limited Partners ownership in Operating Partnership				1,453	(1,453)
Equity compensation associated with Units - Limited Partners					1,959
Net income available to Units - Limited Partners		9,713			9,713
Units - Limited Partners distributions					(7,961)
Change in carrying value of Redeemable Limited Partners					(657)
Unrealized holding (losses) arising during the period	880	880				(223)
Losses reclassified into earnings from other comprehensive income	(5,764)	(5,764)				5,764
Distributions declared per Unit outstanding							0.6025
Net income attributable to Noncontrolling Interests	271,481	271,481						880
Distributions to Noncontrolling Interests								(985)
Balance, end of period at Jun. 30, 2020			37,280	10,627,748	235,169	(67,355)
Balance, end of period at Jun. 30, 2020								4,634
Balance, beginning of year at Dec. 31, 2020			37,280	10,532,037	233,162	(43,666)
Balance, beginning of year at Dec. 31, 2020								4,673
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				66,660	(66,660)
Exercise of EQR share options				39,623
EQR's Employee Share Purchase Plan (ESPP)				2,667
EQR restricted shares				4,814
EQR share options				1,976
EQR ESPP discount				633
Net income available to Units - General Partner		372,380		372,380
OP Units General Partner distributions				(450,220)
Supplemental Executive Retirement Plan (SERP)				(2,057)
Change in market value of Redeemable Limited Partners				(101,966)
Adjustment for Limited Partners ownership in Operating Partnership				(30,807)	30,807
Equity compensation associated with Units - Limited Partners					10,531
Net income available to Units - Limited Partners		13,056			13,056
Units - Limited Partners distributions					(15,999)
Change in carrying value of Redeemable Limited Partners					794
Unrealized holding (losses) arising during the period	1,423	1,423
Losses reclassified into earnings from other comprehensive income	(4,637)	(4,637)				4,637
Distributions declared per Unit outstanding							1.205
Net income attributable to Noncontrolling Interests	388,404	388,404						1,423
Distributions to Noncontrolling Interests								(3,731)
Balance, end of period at Jun. 30, 2021			37,280	10,435,740	205,691	(39,029)
Balance, end of period at Jun. 30, 2021								2,365
Balance, beginning of year at Mar. 31, 2021			37,280	10,318,883	234,969	(41,363)
Balance, beginning of year at Mar. 31, 2021								2,472
Conversion of OP Units held by Limited Partners into OP Units held by General Partner				66,660	(66,660)
Exercise of EQR share options				16,741
EQR's Employee Share Purchase Plan (ESPP)				936
EQR restricted shares				2,540
EQR share options				988
EQR ESPP discount				189
Net income available to Units - General Partner		315,614		315,614
OP Units General Partner distributions				(225,547)
Supplemental Executive Retirement Plan (SERP)				(828)
Change in market value of Redeemable Limited Partners				(29,010)
Adjustment for Limited Partners ownership in Operating Partnership				(31,426)	31,426
Equity compensation associated with Units - Limited Partners					4,043
Net income available to Units - Limited Partners		10,913			10,913
Units - Limited Partners distributions					(7,410)
Change in carrying value of Redeemable Limited Partners					(1,590)
Unrealized holding (losses) arising during the period	741	741
Losses reclassified into earnings from other comprehensive income	(2,334)	(2,334)				2,334
Distributions declared per Unit outstanding							$ 0.6025
Net income attributable to Noncontrolling Interests	$ 328,040	$ 328,040						741
Distributions to Noncontrolling Interests								(848)
Balance, end of period at Jun. 30, 2021			$ 37,280	$ 10,435,740	$ 205,691	$ (39,029)
Balance, end of period at Jun. 30, 2021								$ 2,365