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]	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, 2018			$ 37,280		$ 10,200,910	$ 228,738	$ (64,986)
Balance, beginning of year at Dec. 31, 2018									$ (2,293)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					4,871	(4,871)
Exercise of EQR share options					48,487
EQR's Employee Share Purchase Plan (ESPP)				$ 1,652
Share-based employee compensation expense:
EQR restricted shares					7,982
EQR share options					1,682
EQR ESPP discount					365
Net income available to Units - General Partner		$ 411,962			411,962
OP Units General Partner distributions					(420,916)
Offering costs					(155)
Supplemental Executive Retirement Plan (SERP)					(1,539)
Change in market value of Redeemable Limited Partners					(56,974)
Adjustment for Limited Partners ownership in Operating Partnership					7,771	(7,771)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					4,871	(4,871)
Equity compensation associated with Units - Limited Partners						10,829
Net income available to Units - Limited Partners		15,429				15,429
Units - Limited Partners distributions						(15,079)
Change in carrying value of Redeemable Limited Partners						45
Adjustment for Limited Partners ownership in Operating Partnership					7,771	(7,771)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	$ (33,765)	(33,765)					(33,765)
Losses reclassified into earnings from other comprehensive income	(8,902)	(8,902)					8,902
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 1.135
NONCONTROLLING INTERESTS – PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	430,556	430,556
Contributions by Noncontrolling Interests									4,594
Distributions to Noncontrolling Interests									(5,219)
Net income attributable to Noncontrolling Interests	1,620	1,620							1,620
Balance, end of period at Jun. 30, 2019			37,280		10,206,098	227,320	(89,849)
Balance, end of period at Jun. 30, 2019									(1,298)
Balance, beginning of year at Mar. 31, 2019			37,280		10,084,619	225,081	(75,013)
Balance, beginning of year at Mar. 31, 2019									(5,462)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					84	(84)
Exercise of EQR share options					18,627
EQR's Employee Share Purchase Plan (ESPP)				526
Share-based employee compensation expense:
EQR restricted shares					3,404
EQR share options					889
EQR ESPP discount					98
Net income available to Units - General Partner		308,196			308,196
OP Units General Partner distributions					(210,419)
Offering costs					(155)
Supplemental Executive Retirement Plan (SERP)					(937)
Change in market value of Redeemable Limited Partners					(1,953)
Adjustment for Limited Partners ownership in Operating Partnership					3,119	(3,119)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					84	(84)
Equity compensation associated with Units - Limited Partners						2,926
Net income available to Units - Limited Partners		11,510				11,510
Units - Limited Partners distributions						(7,474)
Change in carrying value of Redeemable Limited Partners						(1,520)
Adjustment for Limited Partners ownership in Operating Partnership					3,119	(3,119)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(19,345)	(19,345)					(19,345)
Losses reclassified into earnings from other comprehensive income	(4,509)	(4,509)					4,509
DISTRIBUTIONS
Distributions declared per Unit outstanding								0.5675
NONCONTROLLING INTERESTS – PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	321,299	321,299
Contributions by Noncontrolling Interests									4,594
Distributions to Noncontrolling Interests									(1,251)
Net income attributable to Noncontrolling Interests	821	821							821
Balance, end of period at Jun. 30, 2019			37,280		10,206,098	227,320	(89,849)
Balance, end of period at Jun. 30, 2019									(1,298)
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
OP Unit Issuance:
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
Share-based employee compensation expense:
EQR restricted shares					7,254
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
LIMITED PARTNERS
Issuance of restricted units to Limited Partners						12
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					3,856	(3,856)
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)
Adjustment for Limited Partners ownership in Operating Partnership					(1,987)	1,987
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(1,190)	(1,190)					(1,190)
Losses reclassified into earnings from other comprehensive income	(11,398)	(11,398)					11,398
DISTRIBUTIONS
Distributions declared per Unit outstanding								1.205
NONCONTROLLING INTERESTS – PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	604,152	604,152
Contributions by Noncontrolling Interests									341
Distributions to Noncontrolling Interests									(10,300)
Net income attributable to Noncontrolling Interests	13,410	13,410							13,410
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
OP Unit Issuance:
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
Share-based employee compensation expense:
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)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					2,012	(2,012)
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)
Adjustment for Limited Partners ownership in Operating Partnership					1,453	(1,453)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(223)	(223)					(223)
Losses reclassified into earnings from other comprehensive income	(5,764)	(5,764)					5,764
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 0.6025
NONCONTROLLING INTERESTS – PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	271,481	271,481
Distributions to Noncontrolling Interests									(985)
Net income attributable to Noncontrolling Interests	$ 880	$ 880							880
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