Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total principal	$ 88,270	$ 69,067
Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	89,095	70,007
Unamortized debt issuance costs	(825)	(940)
Total	88,270	69,067
April 4, 2018 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	25,000	25,000
October 2019 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	21,500	0
January 2020 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	3,573	5,114
February 2020 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	2,963	3,049
January 1, 2023 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	23,640	23,640
September 2023 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	5,131	5,294
July 2026 [Member] | Mortgage Notes Payable [Member]
Debt Instrument [Line Items]
Total principal	$ 7,288	$ 7,910