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v3.25.1

EARNINGS PER COMMON SHARE - Additional Information (Detail) - $ / shares | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Earnings Per Share [Abstract] |  |
Average share price (in dollars per share) | $ 151.64 | $ 145.80

X
- Definition Average Share Price Per Share + References No definition available. + Details
Name: | exr_AverageSharePricePerShare
Namespace Prefix: | exr_
Data Type: | dtr-types1:perShareItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_EarningsPerShareAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration