The net book value of each property at the end of the period.

No definition available.

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- Definition

Represents the number of rental properties encumbered by a lien or mortgage.

+ References

No definition available.

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The amount of depreciation expense related to dispositions that has been reclassified to discontinued operations.

+ References

No definition available.

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- Definition

Gross amount at which new acquisitions and development properties are carried at the end of the period.

+ References

No definition available.

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- Definition

Amount of accumulated depreciation for buildings and furniture and fixtures at the end of the period for each property.

+ References

No definition available.

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- Definition

Total number of properties which the company directly or indirectly through investments in title holding entities owns all or a portion of.

+ References

No definition available.

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- Definition

Total number of units associated with rental properties which the company directly or indirectly through investments in title holding entities owns all or a portion of.

+ References

No definition available.

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- Definition

Gross amount at which dispositions are removed from the balance sheet for properties sold during the year.

+ References

No definition available.

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- Definition

Amount of accumulated depreciation pertaining to real estate investments for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 970

-SubTopic 360

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-Paragraph 1

-Subparagraph (SX 210.12-28.FN4)

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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- Definition

Amount of lien or mortgage outstanding on real estate investment properties for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Regulation S-X (SX)

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- Definition

Amount, before accumulated depreciation, of real estate investments for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Amount of increase in real estate investments related to improvements for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

+ Details

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Amount of depreciation expense of real estate investments for entities with a substantial portion of business acquiring and holding investment real estate.

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Real Estate and Accumulated Depreciation - Overall Summary and Encumbrances Reconciliation (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Overall summary of real estate and accumulated depreciation
Accumulated Depreciation	$ (5,432,805,000)	$ (4,807,709,000)	$ (4,912,221,000)
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	35eqr_NumberOfPropertiesEncumbered
Changes in total real estate
Balance, beginning of year	26,800,948,000us-gaap_RealEstateGrossAtCarryingValue	21,008,429,000us-gaap_RealEstateGrossAtCarryingValue	20,407,946,000us-gaap_RealEstateGrossAtCarryingValue
Acquisitions and development	1,121,423,000	9,273,492,000	1,250,633,000
Improvements	191,243,000us-gaap_RealEstateImprovements	139,950,000us-gaap_RealEstateImprovements	161,460,000us-gaap_RealEstateImprovements
Dispositions and other	(438,231,000)eqr_RealEstateDispositionsAndOther	(3,620,923,000)eqr_RealEstateDispositionsAndOther	(811,610,000)eqr_RealEstateDispositionsAndOther
Balance, end of year	27,675,383,000us-gaap_RealEstateGrossAtCarryingValue	26,800,948,000us-gaap_RealEstateGrossAtCarryingValue	21,008,429,000us-gaap_RealEstateGrossAtCarryingValue
Changes in accumulated depreciation
Balance, beginning of year	(4,807,709,000)	(4,912,221,000)	(4,539,583,000)
Depreciation	758,861,000	1,013,353,000	684,992,000
Dispositions and other	(133,765,000)	(1,117,865,000)	(312,354,000)
Balance, end of year	(5,432,805,000)	(4,807,709,000)	(4,912,221,000)
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	5
EQR-Fanwell 2007 LP [Member] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	0
EQR-Fanwell 2007 LP [Member] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	300,000,000
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	12
EQR-Wellfan 2008 LP [Member] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	0
EQR-Wellfan 2008 LP [Member] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	550,000,000
Fannie Mae Pool 3 [Domain]
Overall summary of real estate and accumulated depreciation
Encumbrances	474,179,543
Real Estate and Accumulated Depreciation Encumbrances Reconciliation [Abstract]
Number of Properties Encumbered	5
Fannie Mae Pool 3 [Domain] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	24,840,581
Fannie Mae Pool 3 [Domain] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	449,338,962
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
Archstone Master Property [Domain] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	0
Archstone Master Property [Domain] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	800,000,000
Individual Property Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	2,962,335,468
Individual Property Encumbrances [Member] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	335,638,681
Individual Property Encumbrances [Member] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	2,626,696,787
EQR-Wholly Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	263
Units	69,217
Investment in Real Estate, Gross	18,538,492,146
Accumulated Depreciation	(3,650,524,741)
Investment in Real Estate Net	14,887,967,405
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(3,650,524,741)
EQR-Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	104
Units	29,923
Investment in Real Estate, Gross	8,113,776,123
Accumulated Depreciation	(1,587,799,207)
Investment in Real Estate Net	6,525,976,916
Encumbrances	4,726,035,749
Changes in accumulated depreciation
Balance, end of year	(1,587,799,207)
Wholly Owned Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	367
Units	99,140
Investment in Real Estate, Gross	26,652,268,269
Accumulated Depreciation	(5,238,323,948)
Investment in Real Estate Net	21,413,944,321
Encumbrances	4,726,035,749
Changes in accumulated depreciation
Balance, end of year	(5,238,323,948)
EQR-Partially Owned Unencumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	8
Units	1,505
Investment in Real Estate, Gross	575,092,221
Accumulated Depreciation	(77,534,358)
Investment in Real Estate Net	497,557,863
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(77,534,358)
EQR-Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Properties	11
Units	2,266
Investment in Real Estate, Gross	448,022,434
Accumulated Depreciation	(116,947,029)
Investment in Real Estate Net	331,075,405
Encumbrances	360,479,262
Changes in accumulated depreciation
Balance, end of year	(116,947,029)
Partially Owned Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	19
Units	3,771
Investment in Real Estate, Gross	1,023,114,655
Accumulated Depreciation	(194,481,387)
Investment in Real Estate Net	828,633,268
Encumbrances	360,479,262
Changes in accumulated depreciation
Balance, end of year	(194,481,387)
Unencumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	271
Units	70,722
Investment in Real Estate, Gross	19,113,584,367
Accumulated Depreciation	(3,728,059,099)
Investment in Real Estate Net	15,385,525,268
Encumbrances	0
Changes in accumulated depreciation
Balance, end of year	(3,728,059,099)
Encumbered Properties [Member]
Overall summary of real estate and accumulated depreciation
Properties	115
Units	32,189
Investment in Real Estate, Gross	8,561,798,557
Accumulated Depreciation	(1,704,746,236)
Investment in Real Estate Net	6,857,052,321
Encumbrances	5,086,515,011
Changes in accumulated depreciation
Balance, end of year	(1,704,746,236)
Total Consolidated Investment in Real Estate [Member]
Overall summary of real estate and accumulated depreciation
Properties	386
Units	102,911
Investment in Real Estate, Gross	27,675,382,924
Accumulated Depreciation	(5,432,805,335)
Investment in Real Estate Net	22,242,577,589
Encumbrances	5,086,515,011
Changes in accumulated depreciation
Balance, end of year	(5,432,805,335)
Total Consolidated Investment in Real Estate [Member] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	360,479,262
Total Consolidated Investment in Real Estate [Member] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	4,726,035,749
Portfolio Entity Encumbrances [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	2,124,179,543
Portfolio Entity Encumbrances [Member] \| Partially Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	24,840,581
Portfolio Entity Encumbrances [Member] \| Wholly Owned Encumbered [Member]
Overall summary of real estate and accumulated depreciation
Encumbrances	$ 2,099,338,962