Restructuring Costs - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		17 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	May 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 24	$ 1,506	$ 183	$ 2,734
2019 French Restructuring Obligation
Restructuring Cost and Reserve [Line Items]
Restructuring costs		1,939		1,939
Fixed asset impairment				525
Benefit related to the reversal of retirement indemnity obligation		1,000		1,000
Restructuring reserve	263	1,102	263	1,102		$ 1,922	$ 0
2019 French Restructuring Obligation | Accrued Liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	263		263
2019 Corporate Restructuring Obligations
Restructuring Cost and Reserve [Line Items]
Restructuring costs		435		963
Restructuring reserve	746	$ 343	746	343		$ 1,080	$ 0
Severance costs					$ 3,000
Benefit related to the reversal of retirement indemnity obligation	$ (976)			(1,396)
Employee Severance | 2019 French Restructuring Obligation
Restructuring Cost and Reserve [Line Items]
Restructuring costs				$ 2,414
Employee Severance | Corporate Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Expected number of positions eliminated (as a percent)		50.00%		50.00%
Employee Severance | 2019 Corporate Restructuring Obligations
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 541	$ 2,359