ACQUISITIONS AND DISPOSITIONS - Asset Acquisitions - Schedule of Operating Properties Acquired (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2025 USD ($) store	Mar. 31, 2025 USD ($) store	Jun. 30, 2024 USD ($) store	Mar. 31, 2024 USD ($) store	Jun. 30, 2025 USD ($) store	Jun. 30, 2024 USD ($) store
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Number of Stores \| store	28	17	3	6	45	9
Cash Paid	$ 161,738	$ 136,025	$ 27,644	$ 35,084	$ 297,763	$ 62,728
Loans Assumed	258,000	0	0	0	258,000	0
Fair Value Adjustment of Debt Assumed	(10,049)	0	0	0	(10,049)	0
Investments in Real Estate Ventures	34,767	105,471	0	0	140,238	0
Net Liabilities/ (Assets) Assumed	4,472	847	97	171	5,319	268
Value of Equity Issued	0	5,878	0	0	5,878	0
Total	$ 448,928	$ 248,221	$ 27,741	$ 35,255	$ 697,149	$ 62,996

Asset Acquisition, Consideration Transferred, Investment In Real Estate Joint Ventures

No definition available.

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

- Definition

Noncash or Part Noncash Acquisition, Fair Value Adjustment Of Debt Assumed

+ References

No definition available.

+ Details

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

- Definition

Represents the number of real estate properties acquired.

+ References

No definition available.

+ Details

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

- Definition

Real Estate Property Asset Acquisition, Consideration Transferred, Equity Interest Issued Or Issuable

+ References

No definition available.

+ Details

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

- Definition

Amount of consideration transferred in asset acquisition. Includes, but is not limited to, cash, liability incurred by acquirer, and equity interest issued by acquirer.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 55
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479908/805-50-55-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480060/805-50-25-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 30
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480027/805-50-30-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 30
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480027/805-50-30-2

+ Details

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

- Definition

Amount of tangible and intangible assets included as part of consideration transferred in asset acquisition, classified as other. Excludes cash.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480060/805-50-25-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 30
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480027/805-50-30-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 30
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480027/805-50-30-2

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_BusinessCombinationAndAssetAcquisitionAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but 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
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-4

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-5

+ Details

Name:	us-gaap_NoncashOrPartNoncashAcquisitionDebtAssumed1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

+ Details

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