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	9 Months Ended
	Sep. 30, 2019 ft² metropolitan_statistical_area storage_unit state property
Schedule of Equity Method Investments [Line Items]
Number of top metropolitan statistical areas for focus of operations \| metropolitan_statistical_area	100
Number of self storage properties \| property	735
Number of states in which self storage properties are located \| state	35
Total rentable square feet in self storage properties \| ft²	46.8
Number of storage units \| storage_unit	376
Consolidated Properties
Schedule of Equity Method Investments [Line Items]
Number of self storage properties \| property	560
Number of states in which self storage properties are located \| state	29
Total rentable square feet in self storage properties \| ft²	34.1
Number of storage units \| storage_unit	273
Unconsolidated Properties \| Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties \| property	175
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 \| storage_unit	103
Company's equity interest in unconsolidated real estate ventures (percent)	25.00%