Accrued Expenses and Other Current Liabilities - Jubilee Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Actuarial assumptions used to calculate the Company's obligations for jubilee payments
Discount rate	1.70%	1.30%
Annual salary increase rate	3.00%	3.00%
Minimum
Actuarial assumptions used to calculate the Company's obligations for jubilee payments
Retirement age for men (in years)	61 years 6 months	61 years 6 months
Retirement age for women (in years)	56 years 6 months	56 years 6 months
Maximum
Actuarial assumptions used to calculate the Company's obligations for jubilee payments
Retirement age for men (in years)	65 years	65 years
Retirement age for women (in years)	65 years	65 years
Other non-current liabilities | Austria
Accrued Expenses and Other Liabilities
Provision for jubilee payments obligation to employees	$ 137	$ 107