Debt Instrument, Number of Extension Periods

No definition available.

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

- Definition

Line Of Credit Facility, Extension Term

+ References

No definition available.

+ Details

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

- Definition

Line of Credit Facility, Accordion Feature, Increase Limit

+ References

No definition available.

+ Details

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

- Definition

Represents the principal amount of recourse debt due to guarantees at the balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	exr_VariableRateComponentAxis=exr_SpecifiedInvestmentGradeRatingAndElectsToUseAlternativeRatesMember
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:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_EurodollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=exr_Tranche1TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=exr_Tranche2TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=exr_Tranche3TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=exr_Tranche4TermLoanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableToBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Notes Payable and Revolving Lines of Credit - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) extension	Dec. 20, 2019 USD ($)	Jul. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 790,000,000
Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1,850,000,000
Increase limit		$ 2,500,000,000		$ 2,000,000,000.0
Number of extension options \| extension	2
Extension term	6 months
Line of Credit \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Line of Credit \| Base rate \| If Company elects to use alternative rates based on specified investment grade rating \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
Line of Credit \| Base rate \| If Company elects to use alternative rates based on specified investment grade rating \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.30%
Line of Credit \| Federal funds rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
Line of Credit \| Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
Line of Credit \| Eurodollar \| If Company elects to use alternative rates based on specified investment grade rating \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.75%
Line of Credit \| Eurodollar \| If Company elects to use alternative rates based on specified investment grade rating \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.25%
Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 650,000,000
Term	4 years
Line of Credit \| Tranche 1 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 480,000,000
Line of Credit \| Tranche 2 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	220,000,000
Line of Credit \| Tranche 3 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	245,000,000		$ 245,000,000
Line of Credit \| Tranche 4 Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	255,000,000		$ 255,000,000
Notes Payable
Debt Instrument [Line Items]
Notes payable	4,343,502,000			$ 4,167,249,000
Notes payable subject to recourse	$ 2,012,791,000