Accrued expenses and other current liabilities, other non-current expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued expenses and other current liabilities, other non-current expenses
Accruals for services provided by vendors-not yet billed	$ 2,404	$ 2,348
Personnel related accruals and liabilities	3,858	5,646
Other current liabilities	836	844
Total	$ 7,098	$ 8,838