EQUITY IN EARNINGS OF UNCONSOLIDATED REAL ESTATE VENTURES - PURCHASE OF JOINT VENTURE PARTNERS' INTERESTS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		0 Months Ended
Mar. 31, 2013	Mar. 31, 2014 property	Feb. 13, 2013 Extra Space of Eastern Avenue LLC property	Feb. 13, 2013 Extra Space of Montrose Avenue LLC property
Real estate joint ventures of the entity
Ownership interest acquired in joint venture (as a percent)			48.00%	61.00%
Number of properties owned by joint venture		19	1	1
Cash paid for acquiring equity interest in the joint venture			$ 5,979	$ 6,878
Equity ownership prior to the acquisition (as a percent)			52.00%	39.00%
Non-cash gain	$ 2,556		$ 2,215	$ 341

- Definition

Represents the percentage of ownership of common stock or equity participation in the investee prior to acquisition accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

The noncash gain (loss) resulting from the purchase of a joint venture partner's interests.

+ References

No definition available.

+ Details

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

- Definition

Represents the ownership interest acquired in a joint venture partner.

+ References

No definition available.

+ Details

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Namespace Prefix:	exr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of properties owned by the joint venture, which are located in Florida, Illinois, Massachusetts, New York and Rhode Island.

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No definition available.

+ Details

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

- Definition

The cash outflow associated with the purchase of real estate held-for-investment and real estate joint ventures.

+ References

No definition available.

+ Details

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

- Details

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