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 Income (Loss) [Member]	Partially Owned Properties [Member]
Balance, beginning of year - Noncontrolling Interest at Dec. 31, 2012						$ 77,688
Balance, beginning of year at Dec. 31, 2012		50,000	7,432,961	159,606	(193,148)
OP Unit Issuance:
Conversion of OP Units held by Limited Partners into OP Units held by General Partner			1,203	(1,203)
Issuance of OP Units			1,929,868
Exercise of EQR share options			16,044
Stock Issued During Period, Value, Employee Stock Purchase Plan			2,973
Share-based employee compensation expense:
EQR restricted shares			10,250
EQR share options			8,684
EQR ESPP discount			557
Offering costs			(954)
Net income available to Units - General Partner			1,716,528
OP Units - General Partner distributions			(432,280)
Supplemental Executive Retirement Plan (SERP)			(439)
Change in market value of Redeemable Limited Partners			69,344
Adjustment for Limited Partners ownership in Operating Partnership			(36,710)	36,710
Issuance of LTIP Units to Noncontrolling Interests				5
Equity compensation associated with Units - Limited Partners				11,542
Net income available to Units - Limited Partners				70,947
Units - Limited Partners distributions				(17,060)
Change in carrying value of Redeemable Limited Partners				(47,029)
Other comprehensive income (loss) - derivative instruments:
Unrealized holding gains (losses) arising during the period	8,737				8,737
Losses reclassified into earnings from other comprehensive income	(16,084)				16,084
Other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	554				554
(Gain) Loss on Sale of Securities, Net	(830)				(830)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(789)				(789)
Net (Income) Attributable to Noncontrolling Interest	70,947					(1,101)
Contributions by Noncontrolling Interests	11,520					11,520
Archstone Acquisition Noncontrolling Interests Partially Owned Properties						28,263
Distributions to Noncontrolling Interests						(5,735)
Balance, end of period - Noncontrolling Interest at Sep. 30, 2013						110,635
Balance, end of period at Sep. 30, 2013		$ 50,000	$ 10,718,029	$ 213,518	$ (169,392)