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) - USD ($)							1 Months Ended	12 Months Ended
	Jul. 23, 2021	Mar. 22, 2021	Dec. 31, 2020	Oct. 06, 2020	Sep. 22, 2020	Feb. 27, 2019	Oct. 06, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	May 19, 2021
Class of Stock [Line Items]
Preferred units stated value (in dollars per share)			$ 0.01					$ 0.01	$ 0.01
Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)								700,326	892,070	581,001
Issuance of shares/units (in shares)									2,622,892	2,412,770
OP units \| Reinsurance Company
Class of Stock [Line Items]
Shares issued in connection with business acquisition (in shares)								96,256
Subordinated performance units
Class of Stock [Line Items]
Conversion Of Stock, Period Prior To Conversion For Conversion Metric								1 year
Percentage of CAD per unit used in conversion rate calculation								110.00%
NSA OP, LP \| Series A-1 preferred units
Class of Stock [Line Items]
Preferred shares dividend rate (percent)								6.00%
Preferred units stated value (in dollars per share)								$ 25.00
Unit conversion ratio								1
Minimum conversion period (in years)								10 years
Redemptions/conversions of units (in shares)								4,000
NSA OP, LP \| Series A-1 preferred units \| Series of Individually Immaterial Asset Acquisitions
Class of Stock [Line Items]
Shares issued in connection with asset acquisition (in shares)								6,665
NSA OP, LP \| OP units
Class of Stock [Line Items]
Unit conversion ratio								1
Minimum conversion period (in years)								1 year
NSA OP, LP \| OP units \| Series of Individually Immaterial Asset Acquisitions
Class of Stock [Line Items]
Shares issued in connection with asset acquisition (in shares)								2,674,928
Issuance of shares/units (in shares)								63,033
NSA OP, LP \| OP units \| Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)								700,326
NSA OP, LP \| Subordinated performance units
Class of Stock [Line Items]
Minimum conversion period (in years)								2 years
Unit conversion, lock out period (in years)								2 years
NSA OP, LP \| Subordinated performance units \| Series of Individually Immaterial Asset Acquisitions
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)								32,741
Issuance of shares/units (in shares)								756,351
NSA OP, LP \| LTIP units
Class of Stock [Line Items]
Unit conversion ratio								1
Issuance of shares/units (in shares)								183,656
Number of units converted (in units)								142,405
DownREIT Partnership \| OP units
Class of Stock [Line Items]
Unit conversion ratio								1
Minimum conversion period (in years)								5 years
DownREIT Partnership \| Subordinated performance units
Class of Stock [Line Items]
Unit conversion ratio								1
Minimum conversion period (in years)								5 years
At the Market Program
Class of Stock [Line Items]
Preferred shares dividend rate (percent)						6.00%
Value of common and preferred shares authorized under ATM program						$ 250,000,000					$ 400,000,000
Value of remaining available offered shares											$ 31,000,000
Common Shares \| Common Shares
Class of Stock [Line Items]
Issuance of shares/units (in shares)								19,196,216
Common Shares \| Public Stock Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)					4,500,000
Sale of stock, price per share (USD per share)					$ 33.15
Sale of stock, additional number of shares issued in transaction (in shares)				400,000
Common Shares \| Public Stock Offering - From Third Parties
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,049,490	1,850,510		4,900,000
Proceeds from sale of stock		$ 97,300,000	$ 60,000,000				$ 0
Common Shares \| Follow-On Public Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	10,120,000
Sale of stock, price per share (USD per share)	$ 51.25
Proceeds from sale of stock	$ 497,400,000
Common Shares \| At the Market Program
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)								6,026,726	743,915
Proceeds from sale of stock								$ 306,700,000	$ 22,900,000
Average price per share (in dollars per share)								$ 51.37	$ 33.01
Common Shares \| Underwriter option to purchase
Class of Stock [Line Items]
Sale of stock, price per share (USD per share)				$ 33.15			$ 33.15
Proceeds received by underwriters on sale of stock							$ 162,400,000
Underwriter option to purchase \| Public Stock Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)					675,000
Underwriter option to purchase \| Follow-On Public Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	1,320,000
Series A preferred shares
Class of Stock [Line Items]
Preferred shares dividend rate (percent)								6.00%
Preferred shares per share amount of dividends (in dollars per share)								$ 1.50
Series A preferred shares \| NSA OP, LP
Class of Stock [Line Items]
Preferred shares cash redemption price (in dollars per share)								$ 25.00