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

ORGANIZATION AND NATURE OF OPERATIONS (Details) ft² in Millions	Mar. 31, 2019 ft² storage_unit state property
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned \| property	706
Number of states in which self storage properties are owned \| state	34
Total rentable square feet in self storage properties \| ft²	44.7
Number of storage units owned and operated \| storage_unit	361,000
Consolidated Properties
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned \| property	531
Number of states in which self storage properties are owned \| state	28
Total rentable square feet in self storage properties \| ft²	32.1
Number of storage units owned and operated \| storage_unit	257,000
Unconsolidated Properties \| Unconsolidated Real Estate Ventures \| Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned \| property	175
Number of states in which self storage properties are owned \| state	21
Total rentable square feet in self storage properties \| ft²	12.6
Number of storage units owned and operated \| storage_unit	104,000
Company's equity interest in Joint Venture (percent)	25.00%