Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Assets held for sale - rental properties	$ 0		$ 0				$ 0
Improvements and replacements in excess of threshold, capitalized amount	1,000		$ 1,000
Improvements and replacements, useful life greater than or equal to one year, capitalization threshold (in years)			1 year
Impairment of real estate			$ 0	$ 0
Future minimum rental payments to be received from noncancelable operating leases, current	52,200,000		52,200,000
Future minimum rental payments to be received from noncancelable operating leases, in two years	721,000		721,000
Future minimum rental payments to be received from noncancelable operating leases, thereafter	0		0
Allowance for uncollectible receivables	$ 263,000		$ 263,000				$ 44,000
Minimum distribution percentage of taxable net income excluding net capital gains			90.00%
Distribution percentage of taxable net income not subject to federal corporate income tax			100.00%
Number of years entity may be precluded from REIT qualifications			4 years
Common stock, shares outstanding (in shares)	60,206,977		60,206,977				60,094,623
Convertible Stock
Property, Plant and Equipment [Line Items]
Common stock, shares outstanding (in shares)	50,000	50,000	50,000	50,000	50,000	50,000	50,000	50,000	50,000	50,000
ASU No 2014-09
Property, Plant and Equipment [Line Items]
Revenue recognized from contract with customer liability	$ 19,000	$ 28,000	$ 55,000	$ 120,000
ASU No. 2016-13
Property, Plant and Equipment [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		true
ASU No. 2018-13
Property, Plant and Equipment [Line Items]
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		true
ASU 2018-19
Property, Plant and Equipment [Line Items]
Change in accounting principle, accounting standards update, early adoption	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2020		Jan. 01, 2020
Change in accounting principle, accounting standards update, immaterial effect	true		true
Minimum | ASU No 2014-09
Property, Plant and Equipment [Line Items]
Revenue recognized over straight line basis term			10 years
Maximum | ASU No 2014-09
Property, Plant and Equipment [Line Items]
Revenue recognized over straight line basis term			12 years
Accounts Payable And Accrued Liabilities | ASU No 2014-09
Property, Plant and Equipment [Line Items]
Contract with customer liability	$ 518,000		$ 518,000				$ 573,000
Texas | Geographic concentration risk
Property, Plant and Equipment [Line Items]
Real estate investment	19.50%		19.50%
Illinois | Geographic concentration risk
Property, Plant and Equipment [Line Items]
Real estate investment	19.00%		19.00%
Colorado | Geographic concentration risk
Property, Plant and Equipment [Line Items]
Real estate investment	15.70%		15.70%
Oregon | Geographic concentration risk
Property, Plant and Equipment [Line Items]
Real estate investment	14.10%		14.10%
Georgia | Geographic concentration risk
Property, Plant and Equipment [Line Items]
Real estate investment	9.00%		9.00%