Description of Business - Additional Information (Details)	12 Months Ended
Dec. 31, 2016 store segment state
Concentration Risk [Line Items]
Number of operating storage facilities in which the entity has equity interests (in stores)	1,016
Number of stores owned by franchisees and third parties	411
Number of operating stores owned and/or managed	1,427
Number of states in which operating storage facilities are located \| state	38
Number of reportable segments \| segment	3
Rental Revenue [Member] \| Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Maximum percentage of rental income accounted for by any single tenant	5.00%

The number of real estate properties owned by franchisees and other third parties as of the balance sheet date.

No definition available.

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Namespace Prefix:	exr_
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Period Type:	instant

- Definition

The number of real estate properties owned and/or managed as of the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	exr_
Data Type:	xbrli:integerItemType
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- 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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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6351-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=64851502&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

+ Details

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- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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

- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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