Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	$ 1,814	$ 2,624
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0	0	$ 140
Deferred Tax Assets, Valuation Allowance	12,065	$ 13,179	$ 7,832	$ 2,006
China
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	3,613
United States
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	13,276
ITALY
Deferred Tax Assets, Valuation Allowance	920
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	$ 3,837