Noncontrolling Interest in Operating Partnership - Schedule of OP Unit Activity (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Noncontrolling Interest [Abstract]
OP Units redeemed for cash (in units)	30,000	23,796
Cash paid for OP Units redeemed	$ 2,558	$ 1,754

Noncontrolling Interest, Operating Partnership Units Redeemed, Cash Paid

No definition available.

Name:	exr_NoncontrollingInterestOperatingPartnershipUnitsRedeemedCashPaid
Namespace Prefix:	exr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant