Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Schedule of OP Unit Activity (Details) - shares	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in units)	5,000	8,862

Noncontrolling Interest, Operating Partnership Units Redeemed For Common Stock

No definition available.

Name:	exr_NoncontrollingInterestOperatingPartnershipUnitsRedeemedForCommonStock
Namespace Prefix:	exr_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration