Commitments and Contingencies (Details) € in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Commitment and Contingencies
Operating leases term, low end of range	1 year	1 year
Operating leases term, high end of range	5 years	5 years
Total lease and rent expense		$ 2,659	$ 2,307	$ 2,227
Foreign exchange hedges liabilities		352
Future minimum payments under operating leases
2017		1,659
2018		1,129
2019		1,018
2020		704
2021		498
Thereafter		0
Accrued Expenses
Commitment and Contingencies
Foreign exchange hedges liabilities		309
Other Liabilities
Commitment and Contingencies
Foreign exchange hedges liabilities		43
Equipment and Construction Contracts
Commitment and Contingencies
Purchase commitment	€ 5,538	$ 8,639