Real Estate Investments - Mortgage Loans Activity (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Mortgage Loans
Originations and fundings under mortgage loans receivable	$ 4,176,000	$ 10,919,000
Scheduled principal payments received	(565,000)	(565,000)
Mortgage loan premium amortization	(3,000)	(3,000)
Provision for loan loss reserve	(36,000)	(104,000)
Net increase in mortgage loans receivable	$ 3,572,000	10,247,000
Mortgage Loans
Mortgage Loans
Loan Term	30 years
Specified basis points for annual increase in interest rate (as a percent)	2.25%
Mortgages With 8.89 Percent Interest With Escalation [Member] | Mortgage Loans
Mortgage Loans
Additions to mortgage loans	$ 2,000
Interest rate (as a percent)	8.89%
Specified basis points for annual increase in interest rate (as a percent)	2.25%
Mortgages with 9.41% Interest, fixed for five years, and escalating by 2.25% thereafter | Mortgage Loans
Mortgage Loans
Additions to mortgage loans		$ 7,500
Interest rate (as a percent)		9.41%
Loan Term		2 years
Specified basis points for annual increase in interest rate (as a percent)		2.25%