Business combination amount paid to acquire joint venture partners interests.

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Equity Method Investment, Ownership Percentage Sold

+ References

No definition available.

+ Details

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- Definition

Net carrying amount of properties distributed.

+ References

No definition available.

+ Details

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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
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Balance Type:	na
Period Type:	instant

- Definition

Number of transferred stores.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Stores Owned

+ References

No definition available.

+ Details

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

- 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=79982066&loc=d3e1392-128463

+ Details

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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=79982066&loc=d3e1392-128463

+ Details

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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

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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=79982066&loc=d3e1392-128463

+ Details

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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

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

- Definition

Amount of gain (loss) on sale or disposal of an equity method investment.

+ References

No definition available.

+ Details

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

- Definition

Amount of the entity's equity method investment which has been sold.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

+ 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 (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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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	9 Months Ended
	Sep. 16, 2016 USD ($) store	Feb. 02, 2016 USD ($) store	Sep. 30, 2016 store	Sep. 30, 2016 USD ($)
ESS PRISA II LLC Joint Venture [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of stores acquired \| store	23
Ownership interest percentage	4.42%
Number of stores owned \| store			42
Equity method ownership percentage sold	4.42%
Equity method investment sold	$ 3,912
Equity method investment gain (loss) on disposal	$ 30,846
Extra Space Properties One Three One LLC [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of transferred stores \| store	23
Net carrying amount of properties distributed	$ 4,326
Business combination, step acquisition, equity interest in acquiree, including subsequent acquisition, percentage	100.00%
Business combination, step acquisition, equity interest in acquiree, fair value	$ 10,988
Equity interest fair value remeasurement non-cash gain	$ 6,662
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
VRS [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Number of stores acquired \| store		6
Ownership interest percentage		45.00%
Prudential Real Estate and Affiliates [Member] \| ESS PRISA II LLC Joint Venture [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Business acquisition, percentage of voting interests acquired	95.58%
Proceeds from the sale of equity method investment	$ 34,758
Prudential Real Estate and Affiliates [Member] \| Extra Space Properties One Three One LLC [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Business acquisition, percentage of voting interests acquired	95.58%
Business combination amount paid to acquire joint venture partner's interest	$ 238,679
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		55.00%
Business combination amount paid to acquire joint venture partner's interest		$ 53,940
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		55.00%
Various States Properties Sept16,2016 [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Real estate assets	$ 248,530
Various States Properties Feb 2, 2016 [Member]
Schedule Of Results Related To Equity Accounted Investees [Line Items]
Real estate assets		$ 98,082