Related Party Transactions and Arrangements - Mortgage Loans Payable (Details) - Affiliated entity - Mortgage loans payable
3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
Property
loan
Jun. 30, 2018
USD ($)
Property
loan
Related Party Transaction [Line Items]    
Number of mortgage loans with related party | loan 4 4
Outstanding principal of related parties notes payable $ 29,400,000 $ 29,400,000
Interest expense on note payable $ 24,500 $ 24,500
Weighted average contractual interest rate 1.00% 1.00%
Weighted average maturity   9 years 5 months 10 days
Commercial Real Estate    
Related Party Transaction [Line Items]    
Number of properties securing loans | Property 6 6