Noncontrolling Interest in Operating Partnership and Other Noncontrolling Interests - Schedule of OP Unit Activity (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Noncontrolling Interest [Abstract]
OP Units redeemed for common stock (in units)	8,862	85,501

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:	instant