Summary of Significant Accounting Policies - Schedule of Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 12,279	$ 19,959	$ 18,587	$ 21,942
Restricted cash	3,139	2,957	3,139	3,251
Cash, cash equivalents, and restricted cash	$ 15,418	$ 22,916	$ 21,726	$ 25,193