Gain(loss) after tax expense (benefit), not previously recognized and resulting from the sale of the company's corporate housing business, which is recognized at the date of sale. A gain (loss) reflects the amount by which the consideration received exceeds (is exceeded by) the net carrying amount (reflecting previous provisions for loss on disposal, if any) of the disposal group.

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Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the sale of the company's corporate housing business subsequent to the balance sheet date.

+ Details

Name:	eqr_DisposalGroupCorporateHousingBusinessSale
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents an estimate of the expenses to be incurred by the Company which are directly related and attributable to reconstructing the garage at one of its properties.

+ Details

Name:	eqr_EstimatesOfLostRevenueAndGarageReconstruction
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents an estimate of the lost revenue and cost of garage reconstruction after the effect of insurance reimbursements that is related to the parking garage collapse.

+ Details

Name:	eqr_EstimatesOfLostRevenueAndGarageReconstructionAfterInsuranceReimbursements
Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the amount of insurance proceeds received which are directly related to the parking garage collapse.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cash inflow received for the settlement of insurance and/ or litigation claims.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of secured debt that the Company assumed in acquiring a property or properties subsequent to the balance sheet date.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of apartment property acquired.

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Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of apartment units acquired.

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Balance Type:	na
Period Type:	duration

- Definition

The total number of rental properties that the company disposed of to unaffiliated parties subsequent to the balance sheet date.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of units associated with the property sold subsequent to the balance sheet date.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with loan origination (the process when securing a mortgage for a piece of real property) or from borrowings to finance the cost of construction received after the balance sheet date but before the financial statements are issued. It is through this process that the terms of the mortgage agreement (amount of loan, interest rate, compounding frequency, and so forth) are established and the involved parties legally bind themselves to the transaction.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the termination of the Company's royalty participation in LRO/Rainmaker.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the amount of expenses incurred by the Company which are directly related to the parking garage collapse.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loan provided by the seller to the buyer at closing.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the sale of a property or properties subsequent to the balance sheet date.

+ Details

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Namespace Prefix:	eqr
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Subsequent Events/Other.

+ Details

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Namespace Prefix:	eqr
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Balance Type:	na
Period Type:	duration

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=6909708&loc=d3e1043-128460

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	credit
Period Type:	instant

- Definition

The expense charged against earnings to eliminate the capitalized costs of projects that have been terminated during the reporting period, which is added back to net income when calculating cash provided by (used in) operations using the indirect method.

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

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-SubTopic 10

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-Subparagraph (b)

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- Definition

The aggregate amount of other expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating expense recognized during the period. Such amounts may include: (a) unusual costs, (b) loss on foreign exchange transactions, (c) losses on securities (net of profits), and (d) miscellaneous other expense items.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 5

-Section 03

-Paragraph 9

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow from the acquisition of residential property intended to generate income for the owner.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-SubTopic 10

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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Subsequent Events/Other (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
Subsequent Events/Other (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Year Project Apartment Property Store Customers OptionPlan State MilitaryHouse	Sep. 30, 2010	Dec. 31, 2010
Subsequent Events/Other (Textuals) [Abstract]
Amount available on the credit facility	$ 1,140,000,000		$ 1,140,000,000
Number of apartment property acquired			4
Number of apartment units acquired			1,000
Value of property acquired			253,900,000
Mortgage loans			12,800,000
Mortgage loan proceeds			38,000,000
Termination of royalty participation			4,500,000
Mortgage debt in conjunction with the acquisition of property			27,600,000
Number Of Properties Disposed Of			1
Number of apartment units sold			385
Value of property sold			30,100,000
Percentage of facility fee paid by the company			0.20%
Acquisition of properties			5,300,000	6,000,000
Write-off of pursuit costs			4,052,000	3,512,000
Other expenses	(2,528,000)	(3,487,000)	(9,318,000)	(9,513,000)
Insurance/Litigation Settlement proceeds				5,200,000
Estimates of lost revenue and garage reconstruction					11,000,000
Estimates Of Lost Revenue And Garage Reconstruction After Insurance Reimbursements					12,000,000
Initial insurance proceeds			2,700,000
Real estate tax and insurance			1,600,000
Net gain on the sale			1,000,000
Sale price of disposed corporate housing business			4,000,000
Loan amount provided to the buyer by the company			$ 2,000,000