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

Annual report pursuant to Section 13 and 15(d)

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details)

INVESTMENT IN UNCONSOLIDATED REAL ESTATE VENTURES - Narrative (Details) $ in Thousands, ft² in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($) property	Dec. 31, 2018 USD ($) ft² storage_unit state property	Dec. 31, 2018 USD ($) ft² storage_unit real_estate_investment_trust state property	Dec. 31, 2017 USD ($) property	Dec. 31, 2016 USD ($) property
Schedule of Equity Method Investments [Line Items]
Total rentable square feet in self storage properties \| ft²		43.0	43.0
Number of storage units \| storage_unit		345,000	345,000
Number of states that self storage properties are in \| state		34	34
Contributions to unconsolidated real estate venture \| $			$ 165,642	$ 15,289	$ 82,950
Number of self storage properties \| property		675	675
Number of self storage properties sold \| property				3
Gross selling price of self storage property sold \| $		$ 5,500	$ 5,500	$ 17,800
Joint Venture [Member] \| 2016 Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of self storage properties \| property					66
Unconsolidated Properties [Member] \| Joint Venture [Member] \| 2018 Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Total rentable square feet in self storage properties \| ft²		7.6	7.6
Number of storage units \| storage_unit		63,000	63,000
Number of self storage properties acquired from 2018 Joint Venture \| property	6
Contributions to unconsolidated real estate venture \| $	$ 64,200		$ 159,900
Number of self storage properties \| property		103	103
Number of acquired properties combined with other properties after acquisition \| property	2
Equity method investment ownership percentage (percent)		25.00%	25.00%
Unconsolidated Properties [Member] \| Joint Venture [Member] \| 2016 Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of self storage properties acquired \| property			3
Total rentable square feet in self storage properties \| ft²		4.9	4.9
Number of storage units \| storage_unit		40,000	40,000
Number of states that self storage properties are in \| state		14	14
Contributions to unconsolidated real estate venture \| $			$ 7,300
Number of self storage properties \| property		73	73
Aggregate purchase price \| $			$ 28,500
Equity method investment ownership percentage (percent)		25.00%	25.00%
Number of self storage properties sold \| property			1
Gross selling price of self storage property sold \| $		$ 9,300	$ 9,300
NSA HHF JV, LLC [Member] \| Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Number of REITs Acquired \| real_estate_investment_trust			2
Aggregate purchase price of Portfolio \| $			$ 1,325,000
Number of self storage properties acquired \| property			112
Total rentable square feet in self storage properties \| ft²		8.2	8.2
Number of storage units \| storage_unit		68,000	68,000
Number of states that self storage properties are in \| state		17	17
Initial capitalization of Joint Venture \| $			$ 639,700
Face amount of 2018 Joint Venture debt financing \| $		$ 643,000	$ 643,000
Interest rate on 2018 Joint Venture debt (percent)		4.34%	4.34%
Term of 2018 Joint Venture debt (in years)		10 years
Heitman America Real Estate REIT LLC [Member] \| Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership percentage (percent)		75.00%	75.00%
Capital contributed to 2018 Joint Venture by JV Investor \| $			$ 479,800