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Related Party Transactions and Arrangements - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Mar. 31, 2017
Mar. 31, 2020
Mar. 31, 2019
Sep. 30, 2019
Dec. 31, 2019
Mar. 01, 2017
Winthrop Advisor and its Affiliates [Member]            
Related Party Transaction [Line Items]            
Fees paid to related parties   $ 350,000 $ 350,000      
Liquidation Value [Member] | Advisor [Member]            
Related Party Transaction [Line Items]            
Cost of assets maximum           $ 3,000,000,000
Liquidation Value [Member] | Advisor [Member] | Post Liquidation Date Agreement Monthly Supplemental Fee [Member]            
Related Party Transaction [Line Items]            
Fees paid to related parties   100,000        
Liquidation Value [Member] | Advisor [Member] | Post Liquidation Date Agreement Quarterly Supplemental Fee [Member]            
Related Party Transaction [Line Items]            
Fees paid to related parties   $ 50,000        
Liquidation Value [Member] | Advisor [Member] | Pre Liquidation Date Agreement Quarterly Supplemental Fee [Member]            
Related Party Transaction [Line Items]            
Fees paid to related parties       $ 25,000    
Liquidation Value [Member] | Service Provider and Affiliates [Member]            
Related Party Transaction [Line Items]            
Asset management fees as a percentage of benchmark           0.325%
Cost of assets maximum           $ 3,000,000,000
Asset management fees earned above           0.25%
Incentive fee, percentage of excess of hurdle amount 10.00%          
Hurdle amount (in dollars per share) $ 110.00          
Liquidation Value [Member] | Winthrop Advisor and its Affiliates [Member] | Asset Management Fees [Member]            
Related Party Transaction [Line Items]            
Asset management fees         $ 1,400,000