Organization - Additional Information (Detail)						9 Months Ended
	May 01, 2018 USD ($) $ / shares shares	Sep. 28, 2017 USD ($) shares	Jan. 27, 2017 USD ($) shares	Oct. 05, 2016 USD ($) shares	Oct. 04, 2016 USD ($) shares	Sep. 30, 2018 USD ($) Property Employee $ / shares shares	Sep. 30, 2017 USD ($)	Dec. 31, 2017 $ / shares shares	Jan. 30, 2017 shares
Organization and Nature of Operations [Line Items]
Date of formation of company						Oct. 04, 2016
Issuance of common stock | $						$ 16,991,578
Gross proceeds from issuance of common stock | $						$ 16,798,588	$ 40,063,542
Number of senior housing properties | Property						4
Number of student housing properties | Property						2
Beneficial interest for ownership percentage						2.60%
Number of employees | Employee						0
Strategic Storage Operating Partnership IV, L.P. [Member]
Organization and Nature of Operations [Line Items]
Date of formation of company						Oct. 05, 2016
Capital contribution | $				$ 1,000
Percentage of common units of limited partnership interest of operating partnership						99.80%
Class A Common Stock [Member]
Organization and Nature of Operations [Line Items]
Number of common stock issued						51,000
Common stock, par value | $ / shares						$ 0.001		$ 0.001
Common stock, shares issued						10,987,493		8,948,551
Common stock, shares authorized						315,000,000		315,000,000	315,000,000
Class T Common Stock [Member]
Organization and Nature of Operations [Line Items]
Number of common stock issued						0
Common stock, par value | $ / shares						$ 0.001		$ 0.001
Common stock, shares issued						0		0
Common stock, shares authorized						315,000,000		315,000,000	315,000,000
Class W Common Stock [Member]
Organization and Nature of Operations [Line Items]
Number of common stock issued						27,000
Common stock, par value | $ / shares						$ 0.001		$ 0.001
Common stock, shares issued						26,809		0
Common stock, shares authorized						70,000,000		70,000,000	70,000,000
Class A, T and W Common Stock [Member]
Organization and Nature of Operations [Line Items]
Gross proceeds from issuance of common stock | $						$ 750,000
Private Offering [Member]
Organization and Nature of Operations [Line Items]
Number of common stock issued			10,800,000
Shares issued pursuant to distribution reinvestment plan			1,000,000
Gross proceeds from issuance of common stock | $			$ 93,000,000
Primary Offering [Member] | Class A Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, par value | $ / shares	$ 10.33
Primary Offering [Member] | Class T Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, par value | $ / shares	10.00
Primary Offering [Member] | Class W Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, par value | $ / shares	9.40
Primary and Public Offering [Member] | Class A Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Shares issuable pursuant to distribution reinvestment plan per share | $ / shares	9.81
Primary and Public Offering [Member] | Class T Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Shares issuable pursuant to distribution reinvestment plan per share | $ / shares	9.50
Primary and Public Offering [Member] | Class W Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Shares issuable pursuant to distribution reinvestment plan per share | $ / shares	$ 9.40
Advisor [Member] | Strategic Storage Operating Partnership IV, L.P. [Member]
Organization and Nature of Operations [Line Items]
Advisor purchased a limited partnership interest in operating partnership | $		$ 199,000		$ 1,000
Advisor agreed to acquire limited partnership interest in operating partnership, number of partnership units		25,447.57		111.11
Capital contribution | $		$ 200,000
Percentage of common units of limited partnership interest of operating partnership						0.20%
Advisor [Member] | Strategic Transfer Agent Services LLC [Member]
Organization and Nature of Operations [Line Items]
Ownership percentage						100.00%
Advisor [Member] | Common Stock [Member]
Organization and Nature of Operations [Line Items]
Number of common stock issued					111.11
Issuance of common stock | $					$ 1,000
SmartStop Asset Management [Member]
Organization and Nature of Operations [Line Items]
Percentage of economic interest owned by sponsor						97.50%
Percentage of voting membership interests owned by sponsor						100.00%
Percentage of property management owned by sponsor						100.00%
SmartStop Asset Management [Member] | Dealer Manager [Member]
Organization and Nature of Operations [Line Items]
Percentage of non-voting equity interest						15.00%
Affiliate [Member] | Strategic Storage Operating Partnership IV, L.P. [Member]
Organization and Nature of Operations [Line Items]
Percentage owned by affiliate						2.50%
Maximum [Member] | Private Offering [Member]
Organization and Nature of Operations [Line Items]
Issuance of common stock | $			100,000,000
Maximum [Member] | Primary Offering [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, shares authorized amount | $	$ 1,000,000,000
Maximum [Member] | Primary Offering [Member] | Class A Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, shares issued	450,000,000
Maximum [Member] | Primary Offering [Member] | Class T Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, shares issued	450,000,000
Maximum [Member] | Primary Offering [Member] | Class W Common Stock [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Common stock, shares issued	100,000,000
Maximum [Member] | Primary and Public Offering [Member] | S-11 Registration Statement [Member]
Organization and Nature of Operations [Line Items]
Shares issuable pursuant to distribution reinvestment plan | $	$ 95,000,000
Minimum [Member] | Private Offering [Member]
Organization and Nature of Operations [Line Items]
Issuance of common stock | $			$ 1,000,000