National Storage Affiliates Trust Quarterly report pursuant to Section 13 or 15(d)

OTHER ASSETS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
OTHER ASSETS - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Customer in-place leases
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 1.7	$ 3.3	$ 7.0	$ 8.6
Management contract
Finite-Lived Intangible Assets [Line Items]
Amortization expense	0.2	0.2	0.7	0.6
Tenant reinsurance intangible
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 0.1	$ 0.2	$ 0.3	$ 0.2