Quarterly report pursuant to Section 13 or 15(d)

Shareholders' Equity - Additional Information (Detail)

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Shareholders' Equity - Additional Information (Detail)
 6 Months Ended
Jan. 15, 2021
Jan. 04, 2021
Jun. 30, 2021
USD ($)
Property
$ / shares
shares
Jun. 30, 2020
USD ($)
Property
$ / shares
shares
Jun. 14, 2018
USD ($)
Aug. 02, 2017
USD ($)
Stockholders Equity [Line Items]            
Number of storage facilities acquired | Property     33 6    
Buyback Program, authorized repurchase amount           $ 200,000,000
Stock repurchased during period, shares | shares     0 0    
Shares issued under dividend reinvestment plan | shares     0 0    
Description of stock split of common stock   three-for-two        
Stock dividend payable percentage of common stock   50.00%        
Description of additional share received Shareholders of record at the close of business on January 15, 2021 received one additional share of Company stock for every two shares owned.          
2018 Equity Program [Member]            
Stockholders Equity [Line Items]            
Common stock value authorized under equity offering program         $ 300,000,000  
Common stock shares issued under equity offering program | shares       285,605    
Weighted average issue price | $ / shares       $ 76.17    
Proceeds from issuance of common stock       $ 21,500,000    
Sales commissions paid       200,000    
Other expenses       $ 100,000    
2020 Equity Program [Member]            
Stockholders Equity [Line Items]            
Common stock value authorized under equity offering program         $ 500,000,000  
Common stock shares issued under equity offering program | shares     3,740,684      
Weighted average issue price | $ / shares     $ 88.91      
Proceeds from issuance of common stock     $ 328,900,000      
Sales commissions paid     3,300,000      
Other expenses     400,000      
2021 Equity Program [Member]            
Stockholders Equity [Line Items]            
Common stock value authorized under equity offering program     $ 500,000,000      
Common stock shares issued under equity offering program | shares     3,740,684