Annual report pursuant to Section 13 and 15(d)

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

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SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Mortgage Loans On Real Estate (Details) - USD ($)
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
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 1,036,660 $ 1,209,736 $ 1,235,000 $ 1,300,000
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 12.00%      
Monthly payment amount $ 14,081      
Face value 1,300,000      
Carrying amount of mortgage 1,036,660      
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 16,250      
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 24,339      
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 14,081      
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 23,859      
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 $ 34,932      
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%