Annual report pursuant to Section 13 and 15(d)

Investment in Joint Ventures - Summary of Company's Unconsolidated Joint Ventures (Parenthetical) (Detail)

v3.8.0.1
Investment in Joint Ventures - Summary of Company's Unconsolidated Joint Ventures (Parenthetical) (Detail)
$ in Thousands
12 Months Ended
Dec. 31, 2017
USD ($)
Property
Facility
Store
Dec. 31, 2016
USD ($)
Property
Dec. 31, 2015
USD ($)
Schedule of Equity Method Investments [Line Items]      
Number of storage facilities acquired | Property 2 122  
Payment for property acquisition $ 22,638    
Mortgages payable 12,674 $ 13,027  
Distributions from unconsolidated joint ventures $ 7,055 5,207 $ 4,821
Storage Facilities [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of storage facilities acquired | Property 0    
Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital $ 100    
Distributions from unconsolidated joint ventures 4,500    
Excess of investment over net asset due to capitalization of acquisition related costs 1,700    
Sovran HHF Storage Holdings II LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Distributions from unconsolidated joint ventures 1,700    
191 III Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Distributions from unconsolidated joint ventures 500    
Iskalo Office Holdings, LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Distributions from unconsolidated joint ventures 200    
Rent paid during the period 1,200 1,200 $ 1,100
SNL/Orix 1200 McDonald Ave., LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Non-recourse mortgage loan principal outstanding 6,400    
SNL/Orix 1200 McDonald Ave., LLC [Member] | Common Stock Shares [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital   400  
SNL/Orix 1200 McDonald Ave., LLC [Member] | Preferred Stock [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital   2,300  
SNL Orix Merrick, LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Non-recourse mortgage loan principal outstanding 9,300    
SNL Orix Merrick, LLC [Member] | Common Stock Shares [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital   400  
SNL Orix Merrick, LLC [Member] | Preferred Stock [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital   2,100  
Review Avenue Partners LLC [Member] | Common Stock Shares [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital 12,500    
N 32nd Street Self Storage, LLC [Member] | Common Stock Shares [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital $ 1,300    
Arizona [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 11    
CO [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 4    
Florida [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 3    
Georgia [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 1    
Georgia [Member] | Life Storage-SERS Storage LLC [Member] | Additional Storage Facilities [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of storage facilities acquired | Property 3    
Payment for property acquisition $ 39,100    
Mortgages payable 22,000    
Contribution of company to joint venture as share in capital $ 3,600    
Kentucky [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 2    
Nevada [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 5    
New Jersey [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 2    
New Jersey [Member] | Sovran HHF Storage Holdings II LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Facility 17    
Ohio [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 6    
Pennsylvania [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 1    
Pennsylvania [Member] | Sovran HHF Storage Holdings II LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Facility 3    
Tennessee [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 2    
Texas [Member] | Sovran HHF Storage Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Property 20    
Texas [Member] | Sovran HHF Storage Holdings II LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Facility 10    
Arizona, Nevada and Tennessee [Member] | Sovran HHF Storage Holdings LLC [Member] | Storage Facilities [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of storage facilities acquired | Facility 18    
Payment for property acquisition $ 330,000    
Mortgages payable $ 135,000    
Number of properties collateral for debt | Store 16    
Contribution of company to joint venture as share in capital $ 39,600    
Arizona, Nevada and Tennessee [Member] | Sovran HHF Storage Holdings LLC [Member] | Storage Facilities [Member] | Mortgage Held By Joint Venture [Member]      
Schedule of Equity Method Investments [Line Items]      
Contribution of company to joint venture as share in capital $ 3,600    
CA [Member] | 191 III Holdings LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of self-storage facilities | Facility 6    
CA [Member] | 191 III Holdings LLC [Member] | Six Storage Facilities [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of storage facilities acquired | Property 6    
Payment for property acquisition $ 104,100    
Mortgages payable 57,200    
Contribution of company to joint venture as share in capital $ 9,300 $ 700