Business combination amount paid to acquire joint venture partners interests.

No definition available.

Name:	exr_BusinessCombinationAmountPaidToAcquireJointVenturePartnersInterests
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Net carrying amount of properties distributed.

+ References

No definition available.

+ Details

Name:	exr_NetCarryingAmountOfPropertiesDistributed
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of acquired stores.

+ References

No definition available.

+ Details

Name:	exr_NumberOfAcquiredStores
Namespace Prefix:	exr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of transferred stores.

+ References

No definition available.

+ Details

Name:	exr_NumberOfTransferredStores
Namespace Prefix:	exr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Real Estate Properties Acquisition [Line Items]

+ References

No definition available.

+ Details

Name:	exr_RealEstatePropertiesAcquisitionLineItems
Namespace Prefix:	exr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Real estate property acquisition fair value of assets acquired.

+ References

No definition available.

+ Details

Name:	exr_RealEstatePropertyAcquisitionFairValueOfAssetsAcquired
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463

+ Details

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

- Definition

Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date.

+ References

No definition available.

+ Details

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeIncludingSubsequentAcquisitionPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463

+ Details

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

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of stores.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfStores
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=exr_VrsSelfStorageLlcJointVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=exr_ExtraSpacePropertiesOneTwoTwoLlcMember
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Data Type:	na
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- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=exr_ESSPRISAIILLCJointVentureMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=exr_ExtraSpaceProperties131LLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=exr_PrudentialRealEstateAndAffiliatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=exr_EssPrisaTwoLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=exr_VariousStatesPropertiesSeptemberSixteenTwoThousandSixteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=exr_VariousStatesPropertiesOneFebruaryTwoTwoThousandAndSixteenMember
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Store Acquisitions and Dispositions - Schedule of Operating Properties Acquired (Additional Information) (Detail) $ in Thousands	Sep. 16, 2016 USD ($) store	Feb. 02, 2016 USD ($) store	Sep. 30, 2016 USD ($)	Sep. 17, 2016 store
Property Acquisitions [Line Items]
Fair Value Real estate assets			$ 821,253
VRS [Member]
Property Acquisitions [Line Items]
Number of stores acquired \| store		6
Equity method ownership percentage		45.04%
ESP 122 [Member]
Property Acquisitions [Line Items]
Number of stores acquired \| store		6
Business acquisition, percentage of voting interests acquired		100.00%
Number of stores transferred to new wholly-owned subsidiary \| store		6
Net carrying amount of properties distributed for spinoff		$ 17,261
Business acquisition, cost of acquired entity, purchase price		44,184
Equity interest fair value remeasurement gain		$ 26,923
PRISA II [Member]
Property Acquisitions [Line Items]
Number of stores acquired \| store	23
Equity method ownership percentage	4.42%
Equity interest fair value remeasurement gain	$ 6,662
ESP 131 [Member]
Property Acquisitions [Line Items]
Number of stores transferred to new wholly-owned subsidiary \| store	23
Net carrying amount of properties distributed for spinoff	$ 4,326
Ownership interest percentage, after acquisition	100.00%
Business acquisition, cost of acquired entity, purchase price	$ 10,988
Equity interest fair value remeasurement gain	$ 6,662
Prudential Real Estate and Affiliates [Member] \| VRS [Member]
Property Acquisitions [Line Items]
Ownership interest percentage, after acquisition		54.96%
Prudential Real Estate and Affiliates [Member] \| ESP 122 [Member]
Property Acquisitions [Line Items]
Total purchase price		$ 53,940
Ownership interest percentage, after acquisition		54.96%
Prudential Real Estate and Affiliates [Member] \| PRISA II [Member]
Property Acquisitions [Line Items]
Business acquisition, percentage of voting interests acquired	95.58%
Prudential Real Estate and Affiliates [Member] \| ESP 131 [Member]
Property Acquisitions [Line Items]
Business acquisition, percentage of voting interests acquired	95.58%
Total purchase price	$ 238,679
PRISA II [Member]
Property Acquisitions [Line Items]
Number of stores \| store				42
Various States Properties Acquired 9/16/2016 [Member]
Property Acquisitions [Line Items]
Fair Value Real estate assets			248,530
Various States Properties Acquired 2/2/2016 [Member]
Property Acquisitions [Line Items]
Fair Value Real estate assets			$ 98,082