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]	OPERATING PARTNERSHIP
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			979	(979)
Issuance of OP Units			1,929,868
Exercise of EQR share options			13,885
Stock Issued During Period, Value, Employee Stock Purchase Plan			2,363
Share-based employee compensation expense:
EQR restricted shares			6,886
EQR share options			6,688
EQR ESPP discount			449
Offering costs			(744)
Net income available to Units - General Partner			1,340,373				1,340,373
OP Units - General Partner distributions			(288,130)
Supplemental Executive Retirement Plan (SERP)			(671)
Change in market value of Redeemable Limited Partners			33,039
Adjustment for Limited Partners ownership in Operating Partnership			(38,718)	38,718
Issuance of LTIP Units to Noncontrolling Interests				5
Equity compensation associated with Units - Limited Partners				9,514
Net income available to Units - Limited Partners				56,111			56,111
Units - Limited Partners distributions				(11,379)
Change in carrying value of Redeemable Limited Partners				(42,557)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	12,337				12,337		12,337
Losses reclassified into earnings from other comprehensive income	12,098				12,098		12,098
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	928				928		928
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	941				941		941
Net Income (Loss) Attributable to Noncontrolling Interest						(790)
Contributions by Noncontrolling Interests						6,769
Archstone Acquisition Noncontrolling Interests Partially Owned Properties						28,263
Distributions to Noncontrolling Interests						(4,437)
Balance, end of period - Noncontrolling Interest at Jun. 30, 2013						107,493
Balance, end of period at Jun. 30, 2013		50,000	10,439,228	209,039	(166,844)
Balance, beginning of year - Noncontrolling Interest at Mar. 31, 2013
Share-based employee compensation expense:
Net income available to Units - General Partner							323,723
Net income available to Units - Limited Partners							12,788
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	9,523						9,523
Losses reclassified into earnings from other comprehensive income	3,826						3,826
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	501						501
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	1,814						1,814
Balance, end of period at Jun. 30, 2013		$ 50,000