Other Assets and Liabilities - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Prepaid Expenses and Other Current Assets:
Valued-added tax recoverable	$ 888	$ 1,206
Prepaid and other expenses	4,837	7,106
Guarantee from Armistice	489	0
Income tax receivable	868	518
Other	124	128
Total	$ 7,206	$ 8,958