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 (LOSS) [Member] ERPOP [Member]	DISTRIBUTIONS	Partially Owned Properties 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
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					356	(356)
Exercise of EQR share options					6,000
EQR's Employee Share Purchase Plan (ESPP)				$ 3,074
Share-based employee compensation expense:
EQR restricted shares					6,804
EQR share options					9,206
EQR ESPP discount					604
Net income available to Units - General Partner		$ 538,030			538,030
OP Units General Partner distributions					(596,735)
Offering costs					(27)
Supplemental Executive Retirement Plan (SERP)					(533)
Change in market value of Redeemable Limited Partners					(14,361)
Adjustment for Limited Partners ownership in Operating Partnership					2,619	(2,619)
LIMITED PARTNERS
Issuance of restricted units to Limited Partners						1
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					356	(356)
Equity compensation associated with Units - Limited Partners						11,074
Net income available to Units - Limited Partners		20,517				20,517
Units - Limited Partners distributions						(21,560)
Change in carrying value of Redeemable Limited Partners						77
Adjustment for Limited Partners ownership in Operating Partnership					2,619	(2,619)
Accumulated other comprehensive income (loss) – derivative instruments:
Unrealized holding gains (losses) arising during the period	$ 24,021	24,021					24,021
Losses reclassified into earnings from other comprehensive income	(13,902)	(13,902)					13,902
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	562,804	562,804							1,939
Contributions by Noncontrolling Interests									125
Distributions to Noncontrolling Interests									(8,930)
Balance, end of period at Sep. 30, 2018			37,280		10,248,833	233,825	(50,689)
Balance, end of period at Sep. 30, 2018									(2,158)
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 1.62
Balance, beginning of year at Jun. 30, 2018			37,280		10,238,467	232,995	(67,310)
Balance, beginning of year at Jun. 30, 2018									(1,646)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					25	(25)
Exercise of EQR share options					3,383
EQR's Employee Share Purchase Plan (ESPP)				893
Share-based employee compensation expense:
EQR restricted shares					1,641
EQR share options					670
EQR ESPP discount					204
Net income available to Units - General Partner		214,164			214,164
OP Units General Partner distributions					(198,939)
Supplemental Executive Retirement Plan (SERP)					5
Change in market value of Redeemable Limited Partners					(14,189)
Adjustment for Limited Partners ownership in Operating Partnership					2,509	(2,509)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					25	(25)
Equity compensation associated with Units - Limited Partners						2,958
Net income available to Units - Limited Partners		8,159				8,159
Units - Limited Partners distributions						(7,186)
Change in carrying value of Redeemable Limited Partners						(567)
Adjustment for Limited Partners ownership in Operating Partnership					2,509	(2,509)
Accumulated other comprehensive income (loss) – derivative instruments:
Unrealized holding gains (losses) arising during the period	12,026	12,026					12,026
Losses reclassified into earnings from other comprehensive income	(4,595)	(4,595)					4,595
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	223,846	223,846							750
Distributions to Noncontrolling Interests									(1,262)
Balance, end of period at Sep. 30, 2018			37,280		10,248,833	233,825	(50,689)
Balance, end of period at Sep. 30, 2018									(2,158)
DISTRIBUTIONS
Distributions declared per Unit outstanding								0.54
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					9,843	(9,843)
Exercise of EQR share options					67,066
EQR's Employee Share Purchase Plan (ESPP)				2,323
Share-based employee compensation expense:
EQR restricted shares					10,304
EQR share options					2,185
EQR ESPP discount					502
Net income available to Units - General Partner		678,295			678,295
OP Units General Partner distributions					(631,635)
Offering costs					(789)
Supplemental Executive Retirement Plan (SERP)					(1,539)
Change in market value of Redeemable Limited Partners					(114,936)
Adjustment for Limited Partners ownership in Operating Partnership					6,919	(6,919)
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					9,843	(9,843)
Equity compensation associated with Units - Limited Partners						12,200
Net income available to Units - Limited Partners		25,339				25,339
Units - Limited Partners distributions						(22,493)
Change in carrying value of Redeemable Limited Partners						(957)
Adjustment for Limited Partners ownership in Operating Partnership					6,919	(6,919)
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	(14,659)	(14,659)					14,659
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	708,402	708,402							2,450
Contributions by Noncontrolling Interests									4,594
Distributions to Noncontrolling Interests									(6,453)
Balance, end of period at Sep. 30, 2019			37,280		10,229,448	226,065	(84,092)
Balance, end of period at Sep. 30, 2019									(1,702)
DISTRIBUTIONS
Distributions declared per Unit outstanding								1.7025
Balance, beginning of year at Jun. 30, 2019			37,280		10,206,098	227,320	(89,849)
Balance, beginning of year at Jun. 30, 2019									(1,298)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					4,972	(4,972)
Exercise of EQR share options					18,579
EQR's Employee Share Purchase Plan (ESPP)				$ 671
Share-based employee compensation expense:
EQR restricted shares					2,322
EQR share options					503
EQR ESPP discount					137
Net income available to Units - General Partner		266,333			266,333
OP Units General Partner distributions					(210,719)
Offering costs					(634)
Change in market value of Redeemable Limited Partners					(57,962)
Adjustment for Limited Partners ownership in Operating Partnership					(852)	852
LIMITED PARTNERS
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					4,972	(4,972)
Equity compensation associated with Units - Limited Partners						1,371
Net income available to Units - Limited Partners		9,910				9,910
Units - Limited Partners distributions						(7,414)
Change in carrying value of Redeemable Limited Partners						(1,002)
Adjustment for Limited Partners ownership in Operating Partnership					(852)	852
Accumulated other comprehensive income (loss) – derivative instruments:
Losses reclassified into earnings from other comprehensive income	(5,757)	(5,757)					5,757
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	$ 277,846	$ 277,846							830
Distributions to Noncontrolling Interests									(1,234)
Balance, end of period at Sep. 30, 2019			$ 37,280		$ 10,229,448	$ 226,065	$ (84,092)
Balance, end of period at Sep. 30, 2019									$ (1,702)
DISTRIBUTIONS
Distributions declared per Unit outstanding								$ 0.5675