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 property acquisition, assets acquired.

+ References

No definition available.

+ Details

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

- Definition

Schedule Of Results Related To Equity Accounted Investees [Line Items]

+ References

No definition available.

+ Details

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

- 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=65885119&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=65885119&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=65885119&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=66011266&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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
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:	us-gaap_RealEstatePropertiesAxis=exr_VariousStatesPropertiesFeb22016Member
Namespace Prefix:
Data Type:	na
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Period Type:

Equity in Earnings of Unconsolidated Real Estate Ventures - Gain on Sale of Real Estate and Purchase of Joint Venture Partner's Interest - Additional Information (Detail) $ in Thousands		3 Months Ended
	Feb. 02, 2016 USD ($) store	Mar. 31, 2016 USD ($)	Mar. 31, 2017 USD ($)
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Fair value, real estate assets			$ 25,556
VRS [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of stores acquired \| store	6
Ownership interest percentage	45.04%
Extra Space Properties One Two Two LLC [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of stores acquired \| store	6
Number of transferred stores \| store	6
Net carrying amount of properties distributed	$ 17,261
Business combination, step acquisition, equity interest in acquiree, including subsequent acquisition, percentage	100.00%
Business combination, step acquisition, equity interest in acquiree, fair value	$ 44,184
Equity interest fair value remeasurement non-cash gain		$ 26,923
Prudential Real Estate and Affiliates [Member] \| VRS [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Business acquisition, percentage of voting interests acquired	54.96%
Prudential Real Estate and Affiliates [Member] \| Extra Space Properties One Two Two LLC [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Business acquisition, percentage of voting interests acquired	54.96%
Business combination amount paid to acquire joint venture partner's interest	$ 53,940
Various States Properties Feb 2, 2016 [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Fair value, real estate assets	$ 98,082