Represents the period over which the average market closing price is measured.

No definition available.

Name:	exr_AverageClosingMarketPriceMeasurementPeriod
Namespace Prefix:	exr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The average closing market price of the entity's common stock.

+ References

No definition available.

+ Details

Name:	exr_CommonStockAverageClosingMarketPrice
Namespace Prefix:	exr_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Note Receivable, Reduction Of Noncontrolling Interests

+ References

No definition available.

+ Details

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

- Definition

Represents the stated interest rate of notes receivable.

+ References

No definition available.

+ Details

Name:	exr_NotesReceivableStatedInterestRate
Namespace Prefix:	exr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Development Stores Owned

+ References

No definition available.

+ Details

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

- Definition

Number Of Operating Stores Owned

+ References

No definition available.

+ Details

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

- Definition

Represents the amount the entity would have paid in cash to redeem the operating partnership units.

+ References

No definition available.

+ Details

Name:	exr_OperatingPartnershipUnitsRedemptionAmount
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the number of consolidated joint ventures as of the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Shareholders' Equity, Units Conversion Ratio

+ References

No definition available.

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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

- Definition

The number of units or equivalent units outstanding for all classes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 5
-Subparagraph (SAB TOPIC 4.F)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

Name:	us-gaap_UnitsOfPartnershipInterestAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=exr_NonControllingInterestOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=exr_CommonOperatingPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
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- Details

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Data Type:	na
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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=stpr_CO
Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_InvestmentTypeAxis=exr_JointVentureTwoMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	srt_StatementGeographicalAxis=stpr_NJ
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PreferredUnitsByNameAxis=exr_SeriesCUnitsMember
Namespace Prefix:
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Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Dec. 31, 2014	Sep. 30, 2019 USD ($) store property joint_venture $ / shares shares	Dec. 31, 2018 USD ($)
Noncontrolling Interest [Line Items]
Period used as a denomination to determine the average closing price of common stock		10 days
Ten day average closing stock price (in dollars per share) \| $ / shares		$ 116.80
OP units outstanding (in units) \| shares		6,025,341
Consideration to be paid on redemption of common OP units		$ 703,760
Operating Partnership
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests		$ 18,524	$ 11,091
Common Stock
Noncontrolling Interest [Line Items]
OP units conversion ratio		1
Other noncontrolling interests
Noncontrolling Interest [Line Items]
Number of consolidated joint ventures \| joint_venture		2
Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest held by entity		90.60%
Ownership percentage in joint venture by joint venture partner		9.40%
Minimum \| Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership percentage in joint venture by joint venture partner		5.00%
Maximum \| Other noncontrolling interests
Noncontrolling Interest [Line Items]
Ownership percentage in joint venture by joint venture partner		20.00%
Texas \| Joint Venture 1
Noncontrolling Interest [Line Items]
Number of operating stores owned \| store		2
Colorado \| Joint Venture 1
Noncontrolling Interest [Line Items]
Number of operating stores owned \| store		2
Pennsylvania \| Joint Venture 2
Noncontrolling Interest [Line Items]
Number of operating stores owned \| property		1
New Jersey \| Joint Venture 2
Noncontrolling Interest [Line Items]
Number of development stores owned \| property		1
Series C Units
Noncontrolling Interest [Line Items]
Note receivable, reduction of noncontrolling interests			$ 8,644
Note receivable interest rate	5.00%