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 [Member] ERPOP [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) ERPOP [Member]	DISTRIBUTIONS	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
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner					134	(134)
Exercise of EQR share options					1,600
EQR’s Employee Share Purchase Plan (ESPP)				$ 1,681
Share-based employee compensation expense:
EQR restricted shares					2,623
EQR share options					7,338
EQR ESPP discount					297
Net income available to Units – General Partner		$ 211,036			211,036
OP Units General Partner distributions					(198,928)
Offering costs					(26)
Supplemental Executive Retirement Plan (SERP)					83
Change in market value of Redeemable Limited Partners					12,831
Adjustment for Limited Partners ownership in Operating Partnership					(2,839)	2,839
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					134	(134)
Equity compensation associated with Units – Limited Partners						4,803
Net income available to Units – Limited Partners		8,059				8,059
Units – Limited Partners distributions						(7,188)
Change in carrying value of Redeemable Limited Partners						(443)
Adjustment for Limited Partners ownership in Operating Partnership					(2,839)	2,839
Accumulated other comprehensive income (loss) – derivative instruments:
Unrealized holding gains (losses) arising during the period	$ 6,087	6,087					6,087
Losses reclassified into earnings from other comprehensive income	(4,791)	(4,791)					4,791
NONCONTROLLING INTERESTS PARTIALLY OWNED PROPERTIES
Net income attributable to Noncontrolling Interests	220,548	220,548							680
Contributions by Noncontrolling Interests									125
Distributions to Noncontrolling Interests									(4,220)
Balance, end of period at Mar. 31, 2018			37,280		10,329,626	234,628	(77,734)
Balance, end of period at Mar. 31, 2018									1,293
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					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							799
Distributions to Noncontrolling Interests									(3,968)
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