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

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details)

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details) storage_unit in Thousands, ft² in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) ft² storage_unit state property	Dec. 31, 2016 property
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	735
Rentable square feet in self storage properties \| ft²	46.8
Number of storage units \| storage_unit	376
Number of states in which self storage properties are located \| state	35
Number of self storage properties sold	1
Gross sales price of self storage property sold \| $	$ 6.5
Corporate Joint Venture \| 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties		66
Unconsolidated Properties \| Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	175
Rentable square feet in self storage properties \| ft²	12.7
Number of storage units \| storage_unit	103
Number of states in which self storage properties are located \| state	21
Unconsolidated Properties \| Corporate Joint Venture \| 2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	103
Rentable square feet in self storage properties \| ft²	7.8
Number of storage units \| storage_unit	63
Number of states in which self storage properties are located \| state	17
Unconsolidated Properties \| Corporate Joint Venture \| 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	72
Rentable square feet in self storage properties \| ft²	4.9
Number of storage units \| storage_unit	40
Number of states in which self storage properties are located \| state	13
Number of self storage properties sold	1
Gross sales price of self storage property sold \| $	$ 4.1