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Summary of Significant Accounting Policies - Derivative Instruments and Mortgage Debt Measured at Fair Value (Detail) - USD ($)
Jun. 30, 2017
Dec. 31, 2016
Level 1 [Member] | Unsecured Notes [Member]    
Derivatives Fair Value [Line Items]    
Debt instruments measured at fair value $ (26,109,600) $ (26,241,160)
Level 2 [Member] | Interest Rate Cap [Member]    
Derivatives Fair Value [Line Items]    
Interest rate cap 6,390 33,597
Level 2 [Member] | Mortgage Loans [Member]    
Derivatives Fair Value [Line Items]    
Debt instruments measured at fair value $ (290,996,165) $ (281,840,780)