Commitments and Contingencies (Details) (USD $)	9 Months Ended
Sep. 30, 2012
Guarantor Obligations [Line Items]
Number of non-cancelable ground leases	6
Total minimum lease commitments under land leases and operating leases for next five years	$ 1,600,000
Number of communities with indemnification agreements from third parties for potential environmental clean-up costs	3
Comprehensive liabilities insurance, deductible per incident	100,000
Property casualty insurance, deductible per incident	1,000,000
Loan and Construction Completion Guarantee [Member] \| Construction Contracts [Member]
Guarantor Obligations [Line Items]
Maximum exposure of the guarantee	76,000,000
Payment Guarantee [Member] \| Construction Contracts [Member]
Guarantor Obligations [Line Items]
Maximum exposure of the guarantee	$ 46,600,000
Mortgage loan, maturity date	Jul. 01, 2014
Debt instrument, number of extensions	2
Debt instrument, term of extensions options (in years)	1 year

Amount of risk retained by the entity before the insurance arrangement begins to provide coverage.

No definition available.

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Namespace Prefix:	ess_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of extensions in a debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	ess_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of extension in a debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	ess_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of communities with indemnification agreements from third parties for potential environmental clean-up costs.

+ References

No definition available.

+ Details

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Namespace Prefix:	ess_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of non-cancelable ground leases.

+ References

No definition available.

+ Details

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Namespace Prefix:	ess_
Data Type:	xbrli:integerItemType
Balance Type:	na
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- Definition

The total of future contractually required payments on leases defined as operating for the next five years.

+ References

No definition available.

+ Details

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Namespace Prefix:	ess_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of risk retained by the entity before the insurance arrangement begins to provide coverage.

+ References

No definition available.

+ Details

Name:	ess_PropertyCasualtyInsuranceDeductiblePerIncident
Namespace Prefix:	ess_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 13

-Subparagraph b

-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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Stated maturity date of the mortgage loan receivable on real estate, in CCYY-MM-DD format.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 948

-SubTopic 310

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-29)

-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 10

-Section S99

-Paragraph 6

-Subparagraph (SX 210.5-04.(c) Schedule IV)

-URI http://asc.fasb.org/extlink&oid=6882300&loc=d3e5864-122674

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 29

-Article 12

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule IV

-Article 5

+ Details

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Namespace Prefix:	us-gaap_
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