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

Quarterly report pursuant to Section 13 or 15(d)

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details)

SHAREHOLDERS' EQUITY AND NONCONTROLLING INTERESTS - Narrative (Details) - USD ($)							1 Months Ended	3 Months Ended						9 Months Ended	27 Months Ended
	Jul. 23, 2021	Mar. 22, 2021	Dec. 30, 2020	Oct. 06, 2020	Sep. 22, 2020	Feb. 27, 2019	Oct. 06, 2020	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	May 19, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common shares of beneficial interest, par value (in dollars per share)					$ 0.01			$ 0.01						$ 0.01		$ 0.01
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)									121,923	190,248	293,083	292,291	118,961
Series A-1 preferred units \| NSA OP, LP
Class of Stock [Line Items]
Preferred share/unit dividend rate (percent)														6.00%
Preferred units stated value (in dollars per share)								$ 25.00						$ 25.00
Unit conversion ratio														1
Redemptions/conversions of units (in shares)														4,000
OP units \| NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio														1
Minimum conversion period (in years)														1 year
Issuance of shares/units (in shares)														63,033
OP units \| NSA OP, LP \| Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)														652,520
OP units \| NSA OP, LP \| Self Storage Properties
Class of Stock [Line Items]
Issuance of shares/units (in shares)														922,199
OP units \| DownREIT Partnership
Class of Stock [Line Items]
Unit conversion ratio														1
Minimum conversion period (in years)														5 years
LTIP units \| NSA OP, LP
Class of Stock [Line Items]
Unit conversion ratio														1
Issuance of shares/units (in shares)														186,571
Conversion of units (in shares)														142,405
Subordinated performance units
Class of Stock [Line Items]
Time frame prior to conversion for conversion metric (in years)														1 year
Percentage of cash available for distribution used in conversion ratio calculation														110.00%
Subordinated performance units \| NSA OP, LP
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)														32,741
Unit conversion, lock out period (in years)														2 years
Subordinated performance units \| NSA OP, LP \| Self Storage Properties
Class of Stock [Line Items]
Issuance of shares/units (in shares)														695,809
Subordinated performance units \| DownREIT Partnership
Class of Stock [Line Items]
Unit conversion ratio														1
Minimum conversion period (in years)														5 years
Prior Sales Agreement
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program						$ 250,000,000
Preferred share/unit dividend rate (percent)						6.00%
Aggregate gross sales price of shares															$ 219,000,000
Value of remaining available offered shares															31,000,000
Amended At The Market Program
Class of Stock [Line Items]
Value of common and preferred shares authorized under ATM program															$ 400,000,000
Common shares \| Common Shares
Class of Stock [Line Items]
Redemptions/conversions of units (in shares)								340,349
Issuance of shares/units (in shares)								10,902,000	2,390,000	3,692,216	181,915	387,000	125,000
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 (in dollars 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
Sale of stock, price per share (in dollars per share)				$ 33.15			$ 33.15
Proceeds from sale of stock		$ 97,300,000	$ 60,000,000				$ 162,400,000
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 (in dollars 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)								782,000						3,814,726
Proceeds from sale of stock								$ 39,900,000						$ 169,000,000
Average price per share (in dollars per share)								$ 51.82						$ 44.74
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 \| NSA OP, LP
Class of Stock [Line Items]
Preferred units cash redemption price (in dollars per share)								$ 25.00						$ 25.00