Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)

v3.20.2
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition (Details)
 3 Months Ended 6 Months Ended 9 Months Ended
Jun. 30, 2020
USD ($)
property
Jun. 30, 2019
USD ($)
Mar. 31, 2017
USD ($)
Jun. 30, 2020
USD ($)
property
Jun. 30, 2019
USD ($)
Sep. 30, 2018
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2016
property
Disaggregation of Revenue [Line Items]                
Number of self storage properties | property 784     784        
Initial term of unconsolidated real estate venture agreements       4 years        
Performance obligation period of recognition       4 years        
Joint venture | 2016 Joint Venture | Unconsolidated properties                
Disaggregation of Revenue [Line Items]                
Number of self storage properties | property 74     74       66
Tenant Insurance and Tenant Warranty Protection Plan Revenues                
Disaggregation of Revenue [Line Items]                
Revenue $ 2,700,000 $ 2,200,000   $ 5,300,000 $ 4,300,000      
Retail Products and Supplies                
Disaggregation of Revenue [Line Items]                
Revenue 400,000 500,000   800,000 900,000      
Property Management, Call Center, and Platform Fees                
Disaggregation of Revenue [Line Items]                
Revenue 3,200,000 3,200,000   $ 6,400,000 6,400,000      
Property management fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets       6.00%        
Platform fees per unconsolidated real estate venture property per month       $ 1,250        
Call center fees as percent of monthly gross revenues and net sales revenue of unconsolidated real estate venture assets       1.00%        
Acquisition Fees                
Disaggregation of Revenue [Line Items]                
Revenue 400,000 500,000   $ 900,000 1,000,000.0      
Acquisition fee     $ 4,100,000     $ 4,000,000.0    
Acquisition fees received as a percent of gross capitalization of Initial 2016 JV Portfolio     0.65%          
Deferred revenue related to acquisition fees 1,900,000     1,900,000     $ 2,800,000  
Tenant Warranty Protection or Tenant Insurance                
Disaggregation of Revenue [Line Items]                
Revenue $ 1,900,000 $ 1,200,000   $ 3,500,000 $ 2,400,000      
Percent of total warranty protection plan proceeds received per unconsolidated real estate venture property (percent)       50.00%