Annual report pursuant to Section 13 and 15(d)

Related-Party Transactions - Summary of Management Fees, Incentive Fees and Associated Credits and Administration Fees (Detail)

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Related-Party Transactions - Summary of Management Fees, Incentive Fees and Associated Credits and Administration Fees (Detail) - USD ($)
 8 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2018
Dec. 31, 2017
Related Party Transaction [Line Items]      
Base management fee   $ 2,837,000 $ 2,041,000
Incentive fee   0 688,000
Capital gains fee   628,000 0
Credits to fees from Adviser   (1,014,000) (54,000)
Total fees to our Adviser, net   2,451,000 2,675,000
Administration fee   1,275,000 914,000
Payment of management fees     0
Financing fee   83,000 36,000
Total fees to Gladstone Securities   2,407,000 36,000
Crop inventory   0.0 1,528,000
Taxable REIT Subsidiary      
Related Party Transaction [Line Items]      
Base management fee   176,000  
Administration fee   57,000 22,000
Allocation of overhead costs   31,000  
Professional fees $ 207,000 136,000 $ 71,000
Preferred Stock | Series B Preferred Stock      
Related Party Transaction [Line Items]      
Payment of management fees   (2,324,000)  
Gladstone Securities      
Related Party Transaction [Line Items]      
Payment of management fees   $ (2,200,000)  
Affiliate | Gladstone Securities      
Related Party Transaction [Line Items]      
Financing fees as a percent of total financings secured   0.11% 0.13%