CONSOLIDATED STATEMENT OF CHANGES IN CAPITAL OF ERP OPERATING LIMITED PARTNERSHIP (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	PREFERRED SHARES	General Partner [Member]	Limited Partner [Member]	ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME	Partially Owned Properties [Member]
Balance, beginning of year - Noncontrolling Interest at Dec. 31, 2011						$ 74,306
Balance, beginning of year at Dec. 31, 2011		200,000	5,665,733	119,536	(196,718)
Redemption of Preferred Shares Preference Units	(150,000)	(150,000)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner			8,560	(8,560)
Issuance of OP Units			192,296
Exercise of EQR share options			46,781
EQR's Employee Share Purchase Plan (ESPP)			4,944
Share-based employee compensation expense:
EQR restricted shares			6,999
EQR share options			9,854
EQR ESPP discount			884
Offering costs			(2,860)
Premium on Redemption of Preferred Shares Preference Units Original Issuance	5,129		5,129
Net income available to Units - General Partner			460,233
OP Units - General Partner distributions			(305,108)
Supplemental Executive Retirement Plan (SERP)			(407)
Acquisition Noncontrolling Interests Partially Owned Properties			1,219			(1,306)
Change in market value of Redeemable Limited Partners			8,866
Adjustment for Limited Partners ownership in Operating Partnership			35,403	(35,403)
Issuance Of OP Units To Noncontrolling Interests	66,606			66,606
Issuance of LTIP Units to Noncontrolling Interests				5
Equity compensation associated with Units - Limited Partners				4,759
Net income available to Units - Limited Partners				21,646
Units - Limited Partners distributions				(14,258)
Change in carrying value of Redeemable Limited Partners				(6,681)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	(12,337)				(12,337)
Losses reclassified into earnings from other comprehensive income	10,907				10,907
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	394				394
Net Income (Loss) Attributable to Noncontrolling Interest						457
Contributions by Noncontrolling Interests						5,992
Distributions to Noncontrolling Interests						(4,775)
Stockholders' Equity, Other						754
Balance, end of period - Noncontrolling Interest at Sep. 30, 2012						75,428
Balance, end of period at Sep. 30, 2012		$ 50,000	$ 6,138,526	$ 147,650	$ (197,754)