Organization - Additional Information (Detail)
 9 Months Ended
Apr. 13, 2017
$ / shares
Feb. 01, 2017
shares
Jan. 09, 2017
USD ($)
shares
Oct. 01, 2015
USD ($)
$ / shares
Sep. 28, 2015
Class
May 23, 2014
USD ($)
Aug. 02, 2013
USD ($)
shares
Sep. 30, 2017
USD ($)
Employee
$ / shares
shares
May 31, 2017
$ / shares
Dec. 31, 2016
$ / 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      
Sale of common shares               $ 17,311,370      
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.      
Primary Offering | Maximum                      
Organization and Nature of Operations [Line Items]                      
Common stock, value authorized               $ 1,000,000,000      
Primary Offering | Minimum                      
Organization and Nature of Operations [Line Items]                      
Sale of common shares           $ 1,500,000          
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 $ 10.22                    
Class A Common stock | Distribution Reinvestment Plan                      
Organization and Nature of Operations [Line Items]                      
Selling price per share | $ / shares                 $ 10.22    
Class A Common stock | Common Stock                      
Organization and Nature of Operations [Line Items]                      
Sale of common shares               $ 1,028      
Number of common stock issued | shares               1,027,612      
Class A Common stock | Common Stock | Distribution Reinvestment Plan                      
Organization and Nature of Operations [Line Items]                      
Gross proceeds from issuance of common stock               $ 10,400,000      
Number of common stock issued | shares               1,000,000      
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 $ 10.22                    
Class T Common stock | Distribution Reinvestment Plan                      
Organization and Nature of Operations [Line Items]                      
Selling price per share | $ / shares                 $ 10.22    
Class T Common stock | Common Stock                      
Organization and Nature of Operations [Line Items]                      
Sale of common shares               $ 565      
Number of common stock issued | shares               564,591      
Class T Common stock | Common Stock | Distribution Reinvestment Plan                      
Organization and Nature of Operations [Line Items]                      
Gross proceeds from issuance of common stock               $ 1,600,000      
Number of common stock issued | shares               200,000      
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                
Class A Common stock and Class T Common stock                      
Organization and Nature of Operations [Line Items]                      
Number of classes of shares of common stock | Class         2            
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      
Number of shares sold to advisor | shares             100        
Sale of common shares to advisor             $ 1,000        
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%