Annual report pursuant to Section 13 and 15(d)

SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Mortgage Loans On Real Estate (Details)

v3.20.4
SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Mortgage Loans On Real Estate (Details) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Face Value $ 1,300,000      
Carrying Amount of Mortgage 1,209,736 $ 1,235,000 $ 1,300,000 $ 1,500,000
Principal Amount of Loans Subject to Delinquent Principal or Interest $ 0      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Interest Rate 8.50%      
Monthly Payment Amount $ 10,833      
Face Value 1,300,000      
Carrying Amount of Mortgage 1,209,736      
Principal Amount of Loans Subject to Delinquent Principal or Interest 0      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term One        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount 10,833      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term Two        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount 10,833      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term Three        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount 16,250      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term Four        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount 24,375      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term Five        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount 35,509      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Term Six        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Monthly Payment Amount $ 46,347      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Interest Rate, Period One        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Interest Rate 8.50%      
Billings, Dunn and McKenzie Counties, North Dakota (Morlock Well) | First Mortgages | Interest Rate, Period Two        
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]        
Interest Rate 12.00%