Real Estate and Accumulated Depreciation - Overall Summary and Encumbrances Reconciliation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Real Estate and Accumulated Depreciation [Line Items]
Number Of Unconsolidated Projects	3
Land And Depreciable Property Net	$ 15,200,000,000	$ 11,200,000,000
Overall summary of real estate and accumulated depreciation
Accumulated Depreciation	(4,807,709,000)	(4,912,221,000)	(4,539,583,000)
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	38
Changes in total real estate
Balance, beginning of year	21,008,429,000	20,407,946,000	19,702,371,000
Acquisitions and development	9,273,492,000	1,250,633,000	1,721,895,000
Improvements	139,950,000	161,460,000	151,476,000
Dispositions and other	(3,620,923,000)	(811,610,000)	(1,167,796,000)
Balance, end of year	26,800,948,000	21,008,429,000	20,407,946,000
Changes in accumulated depreciation
Balance, beginning of year	(4,912,221,000)	(4,539,583,000)	(4,337,357,000)
Depreciation	1,013,353,000	684,992,000	663,616,000
Dispositions and other	(1,117,865,000)	(312,354,000)	(461,390,000)
Balance, end of year	(4,807,709,000)	(4,912,221,000)	(4,539,583,000)
Partially Owned Unconsolidated Units	1,669
EQR-Fanwell 2007 LP [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	300,000,000
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	6
EQR-Wellfan 2008 LP [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	550,000,000
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	14
Fannie Mae Pool 3 [Domain]
Overall summary of real estate and accumulated depreciation
Encumbrances	485,958,561
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	5
Archstone Master Property [Domain]
Overall summary of real estate and accumulated depreciation
Encumbrances	800,000,000
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	13
Individual Property Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	3,038,206,859
EQR-Wholly Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	253
Units	67,220
Investment in Real Estate, Gross	17,386,901,834
Accumulated Depreciation	(3,177,396,618)
Investment in Real Estate Net	14,209,505,216
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(3,177,396,618)
EQR-Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	112
Units	32,101
Investment in Real Estate, Gross	8,397,867,526
Accumulated Depreciation	(1,457,510,357)
Investment in Real Estate Net	6,940,357,169
Encumbrances	2,703,534,549
Changes in accumulated depreciation
Balance, end of year	(1,457,510,357)
Portfolio Entity Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Properties	0
Units	0
Investment in Real Estate, Gross	0
Accumulated Depreciation	0
Investment in Real Estate Net	0
Encumbrances	2,135,958,561
Changes in accumulated depreciation
Balance, end of year	0
Wholly Owned Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	365
Units	99,321
Investment in Real Estate, Gross	25,784,769,360
Accumulated Depreciation	(4,634,906,975)
Investment in Real Estate Net	21,149,862,385
Encumbrances	4,839,493,110
Changes in accumulated depreciation
Balance, end of year	(4,634,906,975)
EQR-Partially Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	8
Units	1,505
Investment in Real Estate, Gross	573,312,560
Accumulated Depreciation	(69,955,775)
Investment in Real Estate Net	503,356,785
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(69,955,775)
EQR-Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	11
Units	2,247
Investment in Real Estate, Gross	442,866,480
Accumulated Depreciation	(102,846,572)
Investment in Real Estate Net	340,019,908
Encumbrances	334,672,310
Changes in accumulated depreciation
Balance, end of year	(102,846,572)
Partially Owned Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	19
Units	3,752
Investment in Real Estate, Gross	1,016,179,040
Accumulated Depreciation	(172,802,347)
Investment in Real Estate Net	843,376,693
Encumbrances	334,672,310
Changes in accumulated depreciation
Balance, end of year	(172,802,347)
Unencumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	261
Units	68,725
Investment in Real Estate, Gross	17,960,214,394
Accumulated Depreciation	(3,247,352,393)
Investment in Real Estate Net	14,712,862,001
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(3,247,352,393)
Encumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	123
Units	34,348
Investment in Real Estate, Gross	8,840,734,006
Accumulated Depreciation	(1,560,356,929)
Investment in Real Estate Net	7,280,377,077
Encumbrances	5,174,165,420
Changes in accumulated depreciation
Balance, end of year	(1,560,356,929)
Total Consolidated Investment in Real Estate [Member]
Overall summary of real estate and accumulated depreciation
Properties	384
Units	103,073
SEC Schedule III, Real Estate and Accumulated Depreciation, Initial Cost of Land	6,887,475,376
Real Estate and Accumulated Depreciation, Initial Cost of Buildings and Improvements	18,679,961,107
Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Building And Fixtures	1,233,511,917
SEC Schedule III, Real Estate and Accumulated Depreciation, Carrying Amount of Land	6,887,475,376
Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements And Furnitures And Fixtures	19,913,473,024
Real Estate And Accumulated Depreciation Carrying Amount Of Land And Buildings And Improvements And Furnitures And Fixtures	26,800,948,400
Investment in Real Estate, Gross	26,800,948,400
Accumulated Depreciation	(4,807,709,322)
Investment in Real Estate Net	21,993,239,078
Encumbrances	5,174,165,420
Changes in accumulated depreciation
Balance, end of year	$ (4,807,709,322)