National Storage Affiliates Trust Annual report pursuant to Section 13 and 15(d)

ORGANIZATION AND NATURE OF OPERATIONS - Narrative (Details) storage_unit in Thousands, ft² in Millions	12 Months Ended
	Dec. 31, 2020 ft² property state metropolitan_statistical_area storage_unit
Real Estate Properties [Line Items]
Number of top metropolitan statistical areas for focus of operations \| metropolitan_statistical_area	100
Number of self storage properties	821
Number of states in which self storage properties are located \| state	36
Total rentable square feet in self storage properties \| ft²	52.0
Number of storage units	413,000
Consolidated properties
Real Estate Properties [Line Items]
Number of self storage properties	644
Number of states in which self storage properties are located \| state	33
Total rentable square feet in self storage properties \| ft²	39.3
Number of storage units \| storage_unit	309
Unconsolidated properties \| Joint Venture
Real Estate Properties [Line Items]
Number of self storage properties	177
Number of states in which self storage properties are located \| state	21
Total rentable square feet in self storage properties \| ft²	12.7
Number of storage units	104,000