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

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	1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($) ft² storage_unit property state	Sep. 30, 2018 USD ($) ft² storage_unit property real_estate_investment_trust state	Sep. 30, 2018 USD ($) ft² storage_unit property state	Sep. 30, 2017 USD ($)	Dec. 31, 2016 property
Schedule of Equity Method Investments [Line Items]
Rentable square feet in self storage properties \| ft²	42.5	42.5	42.5
Number of storage units owned and operated \| storage_unit	341	341	341
Number of states in which self storage properties are owned \| state	34	34	34
Payments to acquire self storage properties \| $			$ 165,642,000	$ 12,647,000
Number of self storage properties	668	668	668
Number of self storage properties sold			2
Gross selling price of self storage properties sold \| $	$ 5,500,000	$ 5,500,000	$ 5,500,000
Joint Venture \| 2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties	103	103	103
Joint Venture \| 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties					66
Unconsolidated Properties \| Joint Venture
Schedule of Equity Method Investments [Line Items]
Proportionate share of Joint Venture (percent)	25.00%	25.00%	25.00%
Unconsolidated Properties \| Joint Venture \| 2018 Joint Venture
Schedule of Equity Method Investments [Line Items]
Rentable square feet in self storage properties \| ft²	7.6	7.6	7.6
Number of storage units owned and operated \| storage_unit	63	63	63
Number of self storage properties acquired from Joint Venture	6
Payments to acquire self storage properties \| $	$ 64,200,000	$ 159,900,000
Number of self storage properties	103	103	103
Number of acquired properties combined with other properties after acquisition	2
Proportionate share of Joint Venture (percent)	25.00%	25.00%	25.00%
Unconsolidated Properties \| Joint Venture \| 2016 Joint Venture
Schedule of Equity Method Investments [Line Items]
Number of self storage properties acquired by the Joint Venture			3
Rentable square feet in self storage properties \| ft²	4.9	4.9	4.9
Number of storage units owned and operated \| storage_unit	40	40	40
Number of states in which self storage properties are owned \| state	14	14	14
Payments to acquire self storage properties \| $			$ 7,300,000
Number of self storage properties	73	73	73
Aggregate purchase price of properties acquired by the Joint Venture \| $			$ 28,500,000
Number of self storage properties sold			1
Gross selling price of self storage properties sold \| $	$ 9,300,000	$ 9,300,000	$ 9,300,000
NSA HHF JV, LLC \| Joint Venture
Schedule of Equity Method Investments [Line Items]
Number REITS acquired \| real_estate_investment_trust		2
Aggregate purchase price of Portfolio \| $		$ 1,325,000,000
Number of self storage properties acquired by the Joint Venture		112
Rentable square feet in self storage properties \| ft²	8.2	8.2	8.2
Number of storage units owned and operated \| storage_unit	68	68	68
Number of states in which self storage properties are owned \| state	17	17	17
Initial capitalization of Joint Venture \| $		$ 639,700,000
Face amount of Joint Venture debt financing \| $	$ 643,000,000	$ 643,000,000	$ 643,000,000
Interest rate on Joint Venture debt (percent)	4.34%	4.34%	4.34%
Term of Joint Venture debt		10 years
Heitman America Real Estate REIT LLC \| Joint Venture
Schedule of Equity Method Investments [Line Items]
Capital contributed to Joint Venture \| $		$ 479,800,000
Proportionate share of Joint Venture (percent)	75.00%	75.00%	75.00%