Real Estate Investments Acquisitions And Sales Of Real Estate (Details) (USD $)	12 Months Ended	3 Months Ended
Dec. 31, 2014 unit community	Dec. 31, 2013 community unit	Dec. 31, 2012 unit community	Mar. 31, 2013
Schedule of Equity Method Investments [Line Items]
Number of Businesses Acquired	6us-gaap_NumberOfBusinessesAcquired	6us-gaap_NumberOfBusinessesAcquired
Number Of Units Acquired	1,480ess_NumberOfUnitsAcquired	1,079ess_NumberOfUnitsAcquired
Payments to Acquire Real Estate	$ 387,547,000us-gaap_PaymentsToAcquireRealEstate	$ 348,774,000us-gaap_PaymentsToAcquireRealEstate	$ 393,771,000us-gaap_PaymentsToAcquireRealEstate
Number of communities sold	4ess_NumberOfCommunitiesSold	3ess_NumberOfCommunitiesSold	2ess_NumberOfCommunitiesSold
Number of units sold	594ess_NumberOfUnitsSold	363ess_NumberOfUnitsSold	264ess_NumberOfUnitsSold
Sales of Real Estate	120,400,000us-gaap_SalesOfRealEstate	57,500,000us-gaap_SalesOfRealEstate	28,300,000us-gaap_SalesOfRealEstate
Gain on sale of real estate	43,600,000us-gaap_GainLossOnSaleOfProperty	29,200,000us-gaap_GainLossOnSaleOfProperty	10,900,000us-gaap_GainLossOnSaleOfProperty
Palo Alto, California [Member]
Schedule of Equity Method Investments [Line Items]
Gain on sale of real estate				1,500,000
Proceeds from Sale of Property Held-for-sale				9,100,000
Apartment Building [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Real Estate	$ 460,700,000	$ 349,100,000

The number of communities sold by the entity during the period.

No definition available.

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

- Definition

Number of units acquired.

+ References

No definition available.

+ Details

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

- Definition

The number of units sold by the entity during the period.

+ References

No definition available.

+ Details

Name:	ess_NumberOfUnitsSold
Namespace Prefix:	ess_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of gain (loss) on sale or disposal of oil and gas property or timber property.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

The number of businesses acquired by the entity during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfBusinessesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the sale of formerly productive land held for sale, anything permanently fixed to it, including buildings, structures on it, and so forth.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfPropertyHeldForSale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Revenue from the sale of commercial, industrial, or residential property during the period. This element is more likely than not relevant to an entity for which real estate operations are a principal activity. If real estate operations are not a principal activity, the reporting entity would likely use a gain (loss) on sale of property, plant, or equipment type element.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(e))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Details

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- Details

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