Organization - Additional Information (Detail)							3 Months Ended
	Apr. 19, 2018 $ / shares	Feb. 01, 2017 shares	Jan. 09, 2017 USD ($) shares	Oct. 01, 2015 USD ($) $ / shares	May 23, 2014 USD ($)	Aug. 02, 2013 USD ($)	Mar. 31, 2018 USD ($) Employee StorageFacility State $ / shares shares	May 31, 2018 $ / shares	Dec. 31, 2017 $ / shares shares	Nov. 30, 2016 shares
Organization And Nature Of Operations [Line Items]
Date of formation of company							Jan. 08, 2013
Preferred Stock, shares authorized | shares							200,000,000		200,000,000
Preferred Stock, par value | $ / shares							$ 0.001		$ 0.001
Shares issuable pursuant to distribution reinvestment plan							$ 95,000,000
Number of self storage facilities | StorageFacility							83
Number of states located for self storage facilities | State							14
Investments in Majority-owned Subsidiaries
Organization And Nature Of Operations [Line Items]
Percentage of non-voting equity owned							15.00%
Investments in Majority-owned Subsidiaries | Affiliates
Organization And Nature Of Operations [Line Items]
Percentage owned by affiliates							2.50%
Distribution Reinvestment Plan
Organization And Nature Of Operations [Line Items]
Common Stock, shares authorized | shares										100,900,000
Description for termination of offering							The DRP Offering may be terminated at any time upon 10 days’ prior written notice to stockholders.
Class A Common stock
Organization And Nature Of Operations [Line Items]
Common Stock, shares authorized | shares							350,000,000		350,000,000
Common Stock, par value | $ / shares							$ 0.001		$ 0.001
Estimated value per common share | $ / shares	$ 10.65
Class A Common stock | Distribution Reinvestment Plan
Organization And Nature Of Operations [Line Items]
Selling price per share | $ / shares								$ 10.65
Class A Common stock | Common Stock | Distribution Reinvestment Plan
Organization And Nature Of Operations [Line Items]
Gross proceeds from issuance of common stock							$ 17,300,000
Number of common stock issued | shares							1,700,000
Class A Common stock | Primary Offering | Common Stock
Organization And Nature Of Operations [Line Items]
Number of shares issued in offering | shares			48,000,000
Gross proceeds from issuance of common stock			$ 493,000,000
Class T Common stock
Organization And Nature Of Operations [Line Items]
Common Stock, shares authorized | shares							350,000,000		350,000,000
Common Stock, par value | $ / shares							$ 0.001		$ 0.001
Estimated value per common share | $ / shares	$ 10.65
Class T Common stock | Distribution Reinvestment Plan
Organization And Nature Of Operations [Line Items]
Selling price per share | $ / shares								$ 10.65
Class T Common stock | Common Stock | Distribution Reinvestment Plan
Organization And Nature Of Operations [Line Items]
Gross proceeds from issuance of common stock							$ 2,600,000
Number of common stock issued | shares							300,000
Class T Common stock | Primary Offering | Common Stock
Organization And Nature Of Operations [Line Items]
Number of shares issued in offering | shares			7,000,000
Gross proceeds from issuance of common stock			$ 73,000,000
SS Toronto | Toronto Five Property Portfolio Merger | Class A Units of Operating Partnership
Organization And Nature Of Operations [Line Items]
Business acquisition partnership units issued | shares		483,197
SmartStop Asset Management | Strategic Storage Trust Advisor II, LLC
Organization And Nature Of Operations [Line Items]
Economic Interests							97.50%
Percentage of voting membership interest							100.00%
SmartStop Asset Management | Property Management Agreement
Organization And Nature Of Operations [Line Items]
Percentage of voting membership interest							100.00%
SmartStop Self Storage, Inc.
Organization And Nature Of Operations [Line Items]
Sale price per share | $ / shares				$ 13.75
Enterprise value on sale				$ 1,400,000,000
Strategic Storage Advisor II, LLC
Organization And Nature Of Operations [Line Items]
Number of employees | Employee							0
Strategic Storage Operating Partnership II, L.P.
Organization And Nature Of Operations [Line Items]
Date of formation of company							Jan. 09, 2013
Advisor purchased a limited partnership interest in Operating Partnership						$ 200,000
Initial capital contribution						$ 1,000
Percentage of limited partnership interests							99.10%
Percentage of limited partnership interests owned by noncontrolling owners							0.90%
Maximum | Primary Offering
Organization And Nature Of Operations [Line Items]
Common stock, value authorized							$ 1,000,000,000
Minimum | Primary Offering
Organization And Nature Of Operations [Line Items]
Sale of common shares					$ 1,500,000