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Summary of Significant Accounting Policies - Narrative (Details)
Sep. 30, 2019
USD ($)
Jan. 01, 2019
lease_option
Dec. 31, 2018
USD ($)
Significant Accounting Policies [Line Items]      
Accounts receivable, net representing rental income accrued $ 42,700,000   $ 43,300,000
Right-of-use asset 1,800,000    
Operating lease liability 1,800,000    
Minimum      
Significant Accounting Policies [Line Items]      
Allowance for doubtful accounts receivables representing rental income accrued $ 48,400   $ 58,500
Operating lease term of contract   1 year  
Maximum      
Significant Accounting Policies [Line Items]      
Operating lease term of contract   15 years  
Corporate Headquarters      
Significant Accounting Policies [Line Items]      
Number of options to extend lease | lease_option   1  
Lease renewal term   5 years