Restructuring Costs - Severance Obligation (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
2019 French Restructuring Obligation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 248
Payments	(13)
Foreign currency impact	(6)
Restructuring reserve, ending balance	107
2019 French Restructuring Obligation | Employee Severance
Restructuring Reserve [Roll Forward]
Charges (income) for employee severance, benefits and other costs	(122)
2019 Corporate Restructuring Obligations
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	272
Payments	(202)
Restructuring reserve, ending balance	70
2019 Corporate Restructuring Obligations | Employee Severance
Restructuring Reserve [Roll Forward]
Charges (income) for employee severance, benefits and other costs	$ 0