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					4,787	(4,787)
Exercise of EQR share options					29,860
EQR's Employee Share Purchase Plan (ESPP)				$ 1,126
Share-based employee compensation expense:
EQR restricted shares					4,578
EQR share options					793
EQR ESPP discount					267
Net income available to Units - General Partner		$ 103,766			103,766
OP Units General Partner distributions					(210,497)
Supplemental Executive Retirement Plan (SERP)					(602)
Change in market value of Redeemable Limited Partners					(55,021)
Adjustment for Limited Partners ownership in Operating Partnership					4,652	(4,652)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					4,787	(4,787)
Equity compensation associated with Units - Limited Partners						7,903
Net income available to Units - Limited Partners		3,919				3,919
Units - Limited Partners distributions						(7,605)
Change in carrying value of Redeemable Limited Partners						1,565
Adjustment for Limited Partners ownership in Operating Partnership					4,652	(4,652)
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	$ (14,420)	(14,420)					(14,420)
Losses reclassified into earnings from other comprehensive income	(4,393)	(4,393)					4,393
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	109,257	109,257
Distributions to Noncontrolling Interests									(3,968)
Net income attributable to Noncontrolling Interests	799	799							799
Balance, end of period at Mar. 31, 2019			37,280		10,084,619	225,081	(75,013)
Balance, end of period at Mar. 31, 2019									(5,462)
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 0.5675
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					1,844	(1,844)
Exercise of EQR share options					11,151
EQR's Employee Share Purchase Plan (ESPP)				$ 869
Share-based employee compensation expense:
EQR restricted shares					4,023
EQR share options					670
EQR ESPP discount					153
Net income available to Units - General Partner		307,833			307,833
OP Units General Partner distributions					(224,507)
Supplemental Executive Retirement Plan (SERP)					149
Change in market value of Redeemable Limited Partners					111,449
Adjustment for Limited Partners ownership in Operating Partnership					(3,440)	3,440
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					1,844	(1,844)
Equity compensation associated with Units - Limited Partners						5,067
Net income available to Units - Limited Partners		11,535				11,535
Units - Limited Partners distributions						(9,076)
Change in carrying value of Redeemable Limited Partners						(1,391)
Adjustment for Limited Partners ownership in Operating Partnership					(3,440)	3,440
Accumulated other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	(967)	(967)					(967)
Losses reclassified into earnings from other comprehensive income	(5,634)	(5,634)					5,634
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	332,671	332,671
Contributions by Noncontrolling Interests									341
Distributions to Noncontrolling Interests									(9,315)
Net income attributable to Noncontrolling Interests	$ 12,530	$ 12,530							12,530
Balance, end of period at Mar. 31, 2020			$ 37,280		$ 10,565,983	$ 235,580	$ (72,896)
Balance, end of period at Mar. 31, 2020									$ 4,739
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 0.6025