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

ORGANIZATION AND NATURE OF OPERATIONS (Details) storage_unit in Thousands, ft² in Millions	Jun. 30, 2018 ft² storage_unit state property	Dec. 31, 2016 property
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned and operated	551
Number of states in which self storage properties are owned and operated \| state	29
Total rentable square feet in self storage properties \| ft²	34.0
Number of storage units owned and operated \| storage_unit	270
Consolidated Properties
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned and operated	479
Number of states in which self storage properties are owned and operated \| state	26
Total rentable square feet in self storage properties \| ft²	29.0
Number of storage units owned and operated \| storage_unit	230
Joint Venture \| Unconsolidated real estate venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned and operated		66
Company's proportionate share of its Joint Venture (percent)	25.00%
Joint Venture \| Unconsolidated Properties \| Unconsolidated real estate venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties owned and operated	72
Number of states in which self storage properties are owned and operated \| state	13
Total rentable square feet in self storage properties \| ft²	5.0
Number of storage units owned and operated \| storage_unit	40