CONSOLIDATED STATEMENT OF CHANGES IN CAPITAL OF ERP OPERATING LIMITED PARTNERSHIP (USD $)	Total USD ($)	Preferred Stock [Member] USD ($)	General Partner [Member] USD ($)	Limited Partner [Member] USD ($)	Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Partially Owned Properties [Member] USD ($)	Series E Preferred Stock [Member]	Series H Preferred Stock [Member]	Series N Preferred Stock [Member]
Balance, beginning of year at Dec. 31, 2009		$ 208,773,000	$ 4,833,885,000	$ 116,120,000	$ 4,681,000	$ 11,054,000
Preferred Stock Preference Units Dividend Rate Percentage							7.00%	7.00%	6.48%
Payments for Repurchase of Preferred Stock and Preference Stock	877,000	0
Stock Units Redeemed Or Called During Period Value		(834,000)
Conversion Of Series E Cumulative Convertible		(7,378,000)
Conversion Of Series H Cumulative Convertible		(561,000)
OP Unit Issuance:
Stock Issued During Period, Value, Conversion of Convertible Securities			7,939,000
Conversion of OP Units held by Limited Partners into OP Units held by General Partner			19,722,000	(19,722,000)
Issuance of OP Units			291,902,000
Exercise of EQR share options			71,596,000
EQR's Employee Share Purchase Plan (ESPP)			5,112,000
Conversion of EQR restricted shares to LTIP Units			0	0
Share-based employee compensation expense:
EQR restricted shares			9,781,000
EQR share options			7,421,000
EQR ESPP discount			1,290,000
OP Units repurchased and retired			(1,887,000)
Offering costs			(4,657,000)
Premium on Redemption of Preferred Shares Preference Units Original Issuance			0
Net income available to Units - General Partner			269,242,000
OP Units - General Partner distributions			(419,320,000)
Supplemental Executive Retirement Plan (SERP)			8,559,000
Acquisition of Noncontrolling Interests - Partially Owned Properties			(16,888,000)			175,000
Change in market value of Redeemable Limited Partners			(129,918,000)
Adjustment for Limited Partners ownership in Operating Partnership			(5,775,000)	5,775,000
Issuance of OP Units to Noncontrolling Interests				8,245,000
Issuance Of Long Term Incentive Plan Units Into Noncontrolling Interest				0
Equity compensation associated with Units - Limited Partners				2,524,000
Net income available to Units - Limited Partners				13,099,000
Units - Limited Partners distributions				(20,300,000)
Change in carrying value of Redeemable Limited Partners				4,658,000
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding gains (losses) arising during the year	(65,894,000)				(65,894,000)
Losses reclassified into earnings from other comprehensive income	3,338,000				3,338,000
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	57,000				57,000
Net income	295,983,000					(726,000)
Contributions by Noncontrolling Interests						222,000
Distributions to Noncontrolling Interests						(2,952,000)
Stockholders' Equity, Other						218,000
Balance, end of period at Dec. 31, 2010		200,000,000	4,948,004,000	110,399,000	(57,818,000)	7,991,000
Preferred Stock Preference Units Dividend Rate Percentage							7.00%	7.00%	6.48%
Payments for Repurchase of Preferred Stock and Preference Stock	0	0
Stock Units Redeemed Or Called During Period Value		0
Conversion Of Series E Cumulative Convertible		0
Conversion Of Series H Cumulative Convertible		0
OP Unit Issuance:
Stock Issued During Period, Value, Conversion of Convertible Securities			0
Conversion of OP Units held by Limited Partners into OP Units held by General Partner			8,580,000	(8,580,000)
Issuance of OP Units			201,942,000
Exercise of EQR share options			95,322,000
EQR's Employee Share Purchase Plan (ESPP)			5,262,000
Conversion of EQR restricted shares to LTIP Units			(3,934,000)	3,934,000
Share-based employee compensation expense:
EQR restricted shares			9,102,000
EQR share options			9,545,000
EQR ESPP discount			1,194,000
OP Units repurchased and retired			0
Offering costs			(3,596,000)
Premium on Redemption of Preferred Shares Preference Units Original Issuance			0
Net income available to Units - General Partner			879,720,000
OP Units - General Partner distributions			(467,729,000)
Supplemental Executive Retirement Plan (SERP)			10,765,000
Acquisition of Noncontrolling Interests - Partially Owned Properties			(4,784,000)			(8,025,000)
Change in market value of Redeemable Limited Partners			(22,714,000)
Adjustment for Limited Partners ownership in Operating Partnership			(946,000)	946,000
Issuance of OP Units to Noncontrolling Interests				0
Issuance Of Long Term Incentive Plan Units Into Noncontrolling Interest				0
Equity compensation associated with Units - Limited Partners				3,641,000
Net income available to Units - Limited Partners				40,780,000
Units - Limited Partners distributions				(21,434,000)
Change in carrying value of Redeemable Limited Partners				(10,150,000)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding gains (losses) arising during the year	(143,598,000)				(143,598,000)
Losses reclassified into earnings from other comprehensive income	4,343,000				4,343,000
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	355,000				355,000
Net income	935,197,000					832,000
Contributions by Noncontrolling Interests						75,911,000
Distributions to Noncontrolling Interests						(1,163,000)
Stockholders' Equity, Other						(1,240,000)
Balance, end of period at Dec. 31, 2011		200,000,000	5,665,733,000	119,536,000	(196,718,000)	74,306,000
Preferred Stock Preference Units Dividend Rate Percentage							7.00%	7.00%	6.48%
Payments for Repurchase of Preferred Stock and Preference Stock	150,000,000	(150,000,000)
Stock Units Redeemed Or Called During Period Value		0
Conversion Of Series E Cumulative Convertible		0
Conversion Of Series H Cumulative Convertible		0
OP Unit Issuance:
Stock Issued During Period, Value, Conversion of Convertible Securities			0
Conversion of OP Units held by Limited Partners into OP Units held by General Partner			18,929,000	(18,929,000)
Issuance of OP Units			1,388,583,000
Exercise of EQR share options			49,039,000
EQR's Employee Share Purchase Plan (ESPP)			5,399,000
Conversion of EQR restricted shares to LTIP Units			0	0
Share-based employee compensation expense:
EQR restricted shares			8,936,000
EQR share options			11,752,000
EQR ESPP discount			965,000
OP Units repurchased and retired			0
Offering costs			(39,359,000)
Premium on Redemption of Preferred Shares Preference Units Original Issuance	5,100,000		5,129,000
Net income available to Units - General Partner			826,212,000
OP Units - General Partner distributions			(554,429,000)
Supplemental Executive Retirement Plan (SERP)			282,000
Acquisition of Noncontrolling Interests - Partially Owned Properties			1,293,000			(1,306,000)
Change in market value of Redeemable Limited Partners			38,734,000
Adjustment for Limited Partners ownership in Operating Partnership			5,763,000	(5,763,000)
Issuance of OP Units to Noncontrolling Interests				66,606,000
Issuance Of Long Term Incentive Plan Units Into Noncontrolling Interest				5,000
Equity compensation associated with Units - Limited Partners				5,307,000
Net income available to Units - Limited Partners				38,641,000
Units - Limited Partners distributions				(25,095,000)
Change in carrying value of Redeemable Limited Partners				(20,702,000)
Accumulated other comprehensive (loss) income - derivative instruments:
Unrealized holding gains (losses) arising during the year	(11,772,000)				(11,772,000)
Losses reclassified into earnings from other comprehensive income	14,678,000				14,678,000
Accumulated other comprehensive income (loss) - other instruments:
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	664,000				664,000
Net income	881,204,000					844,000
Contributions by Noncontrolling Interests						8,221,000
Distributions to Noncontrolling Interests						(5,131,000)
Stockholders' Equity, Other						754,000
Balance, end of period at Dec. 31, 2012		$ 50,000,000	$ 7,432,961,000	$ 159,606,000	$ (193,148,000)	$ 77,688,000