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

Noncontrolling Interest, Conversion Of Preferred Units to Common Units, Number Of Units Issued

+ References

No definition available.

+ Details

Name:	exr_NoncontrollingInterestConversionOfPreferredUnitstoCommonUnitsNumberOfUnitsIssued
Namespace Prefix:	exr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Note Receivable, Reduction Of Noncontrolling Interests

+ References

No definition available.

+ Details

Name:	exr_NoteReceivableReductionOfNoncontrollingInterests
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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

- Definition

Shareholders' Equity, Units Conversion Ratio

+ References

No definition available.

+ Details

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

- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

+ Details

Name:	us-gaap_ConversionOfStockSharesConverted1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
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

Name:	us-gaap_MinorityInterestLineItems
Namespace Prefix:	us-gaap_
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

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
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

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
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

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

- Details

Name:	us-gaap_StatementEquityComponentsAxis=exr_CommonOperatingPartnershipMember
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:	us-gaap_PreferredUnitsByNameAxis=exr_SeriesCUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=exr_JointVentureOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Noncontrolling Interests In Operating Partnership and Other Noncontrolling Interests - Additional Information (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 01, 2018 shares	Dec. 31, 2018 USD ($) store joint_venture $ / shares shares	Dec. 31, 2017 store	Dec. 31, 2016 store
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		$ 91.64
OP units outstanding (in units)		5,994,251
Consideration to be paid on redemption of common OP units \| $		$ 549,313
Number of owned stores \| store		28	39	8
Operating Partnership
Noncontrolling Interest [Line Items]
Ownership interest held by entity (as a percent)		91.00%
Voting interests of third-party owners		9.00%
Operating Partnership
Noncontrolling Interest [Line Items]
Conversion of units, units issued upon conversion (in shares)	373,113
Reduction of noncontrolling interest for note receivable \| $		$ 11,091
Common Stock
Noncontrolling Interest [Line Items]
Unit conversion ratio		1
Other
Noncontrolling Interest [Line Items]
Number of consolidated joint ventures \| joint_venture		2
Series C Units
Noncontrolling Interest [Line Items]
Conversion of units, units converted (in shares)	407,996
Joint venture one
Noncontrolling Interest [Line Items]
Number of owned stores \| store		2
Minimum \| Other
Noncontrolling Interest [Line Items]
Voting interests of third-party owners		5.00%
Maximum \| Other
Noncontrolling Interest [Line Items]
Voting interests of third-party owners		20.00%