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			684	(684)
Issuance of OP Units			1,929,868
Exercise of EQR share options			7,174
EQR's Employee Share Purchase Plan (ESPP)			1,763
Share-based employee compensation expense:
EQR restricted shares			3,052
EQR share options			3,367
EQR ESPP discount			311
Offering costs			(406)
Net income available to Units - General Partner			1,016,650				1,016,650
OP Units - General Partner distributions			(144,015)
Supplemental Executive Retirement Plan (SERP)			(2,219)
Change in market value of Redeemable Limited Partners			50,109
Adjustment for Limited Partners ownership in Operating Partnership			(42,863)	42,863
Issuance of LTIP Units to Noncontrolling Interests				3
Equity compensation associated with Units - Limited Partners				4,304
Net income available to Units - Limited Partners				43,323			43,323
Units - Limited Partners distributions				(5,691)
Change in carrying value of Redeemable Limited Partners				(38,494)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding (losses) arising during the period	2,814				2,814		2,814
Losses reclassified into earnings from other comprehensive income	8,272				8,272		(8,272)
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	427				427		427
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(873)				(873)		(873)
Net Income (Loss) Attributable to Noncontrolling Interest						25
Contributions by Noncontrolling Interests						3,299
Archstone Acquisition Noncontrolling Interests Partially Owned Properties						28,263
Distributions to Noncontrolling Interests						(3,345)
Balance, end of period - Noncontrolling Interest at Mar. 31, 2013						105,930
Balance, end of period at Mar. 31, 2013		$ 50,000	$ 10,256,436	$ 205,230	$ (182,508)