Unsecured Lines of Credit - Summary of Unsecured Lines of Credit (Details)	12 Months Ended
	Dec. 31, 2020 USD ($)
Line Of Credit Facility [Line Items]
Lines of credit	$ 7,475,000
Unsecured Lines of Credit [Member]
Line Of Credit Facility [Line Items]
Lines of credit	7,475,000
Line of credit facility maximum borrowing capacity	60,000,000
Unsecured Lines of Credit [Member] | 2.65% Interest Bearing Line of Credit [Member] | Bankers Trust Non-operating [Member]
Line Of Credit Facility [Line Items]
Lines of credit	7,475,000
Line of credit facility maximum borrowing capacity	$ 50,000,000
Commitment Maturity	2022-06
Variable / Fixed	Variable	[1]
Reset Frequency	Monthly
Line of credit facility, interest rate during period	2.65%
Unsecured Lines of Credit [Member] | 3.40% Interest Bearing Line of Credit [Member] | Bankers Trust Operating [Member]
Line Of Credit Facility [Line Items]
Line of credit facility maximum borrowing capacity	$ 10,000,000
Commitment Maturity	2022-06
Variable / Fixed	Variable	[1]
Reset Frequency	Monthly
Line of credit facility, interest rate during period	3.40%

[1] The variable rate is indexed to LIBOR plus an applicable margin.