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

Annual report pursuant to Section 13 and 15(d)

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details)

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) $ / shares in Units, $ in Thousands						12 Months Ended
	Jul. 13, 2018 USD ($) $ / shares shares	Dec. 11, 2017 USD ($) $ / shares shares	Oct. 11, 2017 USD ($) $ / shares shares	Dec. 16, 2016 USD ($) $ / shares shares	Jul. 06, 2016 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Class of Stock [Line Items]
Net proceeds from issuance of common shares \| $	$ 175,600	$ 140,300		$ 105,500	$ 237,500	$ 175,616	$ 140,261	$ 378,281
Proceeds from issuance of preferred shares \| $						$ 0	$ 166,566	$ 0
Stated value of series A-1 preferred units \| $ / shares						$ 0.01	$ 0.01
Common Shares [Member] \| Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)		750,000		675,000	1,571,250
Common Shares [Member] \| Follow On Offering [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)	5,900,000	5,750,000		5,175,000	12,046,250
Share price (in dollars per share) \| $ / shares	$ 29.86	$ 25.5		$ 20.48	$ 20.75
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)			6,900,000
Preferred shares dividend rate (percent)			6.00%
Proceeds from issuance of preferred shares \| $			$ 166,600
Preferred shares per share amount of dividends (in dollars per share) \| $ / shares			$ 1.5
Preferred shares redemption price (in dollars per share) \| $ / shares			$ 25
Series A Preferred Shares [Member] \| Over-Allotment Option [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)			900,000
Series A-1 Preferred Units [Member]
Class of Stock [Line Items]
Preferred shares dividend rate (percent)						6.00%
Stated value of series A-1 preferred units \| $ / shares						$ 25.00
NSA OP, LP [Member] \| OP units [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)						2,024,170
Unit conversion ratio						1
Minimum conversion period						1 year
Redemptions of units (in shares)						462,778
NSA OP, LP [Member] \| OP units [Member] \| Acquisition of Self Storage Properties [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)						584,004
NSA OP, LP [Member] \| Subordinated performance units [Member]
Class of Stock [Line Items]
Number of units converted (in units)						929,057
Minimum conversion period						2 years
Redemptions of units (in shares)						997,074
Unit conversion, lock out period						2 years
NSA OP, LP [Member] \| Subordinated performance units [Member] \| Acquisition of Self Storage Properties [Member]
Class of Stock [Line Items]
Issuance of shares/units (in shares)						141,811
NSA OP, LP [Member] \| LTIP units [Member]
Class of Stock [Line Items]
Number of units converted (in units)						9,100
Unit conversion ratio						1
NSA OP, LP [Member] \| Series A-1 Preferred Units [Member]
Class of Stock [Line Items]
Unit conversion ratio						1
DownREIT Partnership [Member] \| OP units [Member]
Class of Stock [Line Items]
Unit conversion ratio						1
Minimum conversion period						5 years
DownREIT Partnership [Member] \| Subordinated performance units [Member]
Class of Stock [Line Items]
Number of units converted (in units)						15,377
Unit conversion ratio						1
Minimum conversion period						5 years