Notes Receivable (Details)	9 Months Ended
	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Aug. 31, 2015 USD ($)	Apr. 16, 2014 property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of agreements to purchase property | property				38
Total outstanding principal	$ 6,650,000	$ 2,780,000
Points paid, net of direct issuance costs	(10,000)	(4,000)
Interest receivable (net prepaid interest)	311,000	67,000
Total notes and interest receivable	6,951,000	2,843,000
Notes receivable	6,700,000	2,800,000
Mortgage Note January 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	1,800,000	1,800,000
Mortgage Note March 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	240,000	$ 980,000
Mortgage Note Two March 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	2,194,000
Mortgage Note April 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	1,647,000
Mortgage Note January 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	100,000
Mortgage Note February 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	$ 669,000
FPI Loan Program | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts			$ 100,000
FPI Loan Program | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt instrument, term	6 years