Notes Receivable (Details)	6 Months Ended
	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Aug. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	$ 11,994,000	$ 9,350,000
Points paid, net of direct issuance costs		(6,000)
Interest receivable (net prepaid interest)	612,000	461,000
Provision for interest receivable	(137,000)	(45,000)
Total notes and interest receivable	$ 12,469,000	9,760,000
Interest rate	7.5
Notes receivable	$ 12,500,000	9,400,000
Mortgage Note Maturing January 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	1,800,000	1,800,000
Mortgage Note Maturing March 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	240,000	240,000
Mortgage Note Two Maturing March 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total outstanding principal	2,194,000	2,194,000
Mortgage Note January 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts	1,647,000	1,647,000
Mortgage Note Maturing January 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts		100,000
Mortgage Note Maturing February 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts		669,000
Mortgage Note Two Maturing January 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts		$ 2,700,000
Mortgage Note Maturing August 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts	5,250,000
Mortgage Note Maturing December 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts	116,000
Line of Credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal amounts	$ 747,000
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