Significant Events and Transactions of the Period - Narrative (Details)				3 Months Ended	9 Months Ended
	May 04, 2020 USD ($)	May 04, 2020 EUR (€)	Feb. 08, 2019 shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 EUR (€) shares	Jun. 30, 2020 USD ($)	Jun. 30, 2020 EUR (€)	Apr. 23, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Jul. 26, 2019 USD ($)	Dec. 31, 2018 shares	Oct. 25, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Treasury stock (in shares) | shares				5,989,258	5,989,258	5,989,258				3,903,673		3,500,000
Treasury stock, retired (in shares) | shares			1,600,000
Marketable securities				$ 23,416,000	$ 23,416,000					$ 0
Revolving credit facility | Amended RCF To The End Of March 2022 Through March 2023 | Line of Credit
Restructuring Cost and Reserve [Line Items]
Revolving credit facility, maximum borrowing capacity				344,000,000	344,000,000	€ 294,000,000
Revolving credit facility | Bank Syndicate RCF | Line of Credit
Restructuring Cost and Reserve [Line Items]
Proceeds from lines of credit	$ 163,900,000	€ 140,000,000
Revolving credit facility, maximum borrowing capacity				245,900,000	245,900,000	€ 210,000,000.0
Investments [Member]
Restructuring Cost and Reserve [Line Items]
Marketable securities				$ 20,000,000.0	$ 20,000,000.0		$ 23,400,000	€ 20,000,000.0
Interest rate percentage				0.75%	0.75%	0.75%	0.25%	0.25%
Closing R&D Operations In Palo Alto
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 60,000.00	$ 560,000
Business exit costs					4,600,000
Closing R&D Operations In Palo Alto | Research and Development expense
Restructuring Cost and Reserve [Line Items]
Business exit costs					1,500,000
Closing R&D Operations In Palo Alto | G&A
Restructuring Cost and Reserve [Line Items]
Business exit costs					800,000
Closing R&D Operations In Palo Alto | Sales and Operations expense
Restructuring Cost and Reserve [Line Items]
Business exit costs					2,300,000
New Organization Structure
Restructuring Cost and Reserve [Line Items]
Restructuring charges				2,800,000	3,932,000
New Organization Structure | Research and Development expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges				0	200,000
New Organization Structure | G&A
Restructuring Cost and Reserve [Line Items]
Restructuring charges				1,300,000	1,300,000
New Organization Structure | Sales and Operations expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 1,500,000	$ 2,400,000
American Depositary Shares
Restructuring Cost and Reserve [Line Items]
Authorized amount of share repurchase program									$ 30,000,000.0		$ 80,000,000.0		$ 80,000,000.0
Treasury stock (in shares) | shares										3,200,000