Represents the number of consolidated joint ventures that were variable interest entities.

No definition available.

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

- Definition

Represents the number of wholly-owned unconsolidated subsidiaries.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for a borrowing supported by a written promise to pay an obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

- Details

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Namespace Prefix:
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- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=exr_ESSStatutoryTrustIIMember
Namespace Prefix:
Data Type:	na
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- Details

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Variable Interests - Additional Information (Detail) $ in Thousands		3 Months Ended	9 Months Ended
	Sep. 28, 2018 USD ($)	Sep. 30, 2018 joint_venture subsidiary	Sep. 30, 2018 USD ($) joint_venture subsidiary	Sep. 30, 2017 USD ($)
Variable Interest Entity [Line Items]
Number of wholly-owned unconsolidated subsidiaries \| subsidiary		3	3
Repayments of debt			$ 21,650	$ 0
Number of interests in consolidated VIE joint ventures \| joint_venture		0	0
Notes payable to Trusts \| Trust II \| Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Repayments of debt	$ 21,650