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Significant Events and Transactions of the Period - Narrative (Details)				3 Months Ended	6 Months Ended
	May 04, 2020 USD ($)	May 04, 2020 EUR (€)	Feb. 08, 2019 shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2020 EUR (€) shares	Apr. 23, 2020 USD ($)	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				5,589,408	5,589,408	5,589,408		3,903,673		3,500,000
Treasury stock, retired (in shares) \| shares			1,600,000
Marketable securities				$ 22,396,000	$ 22,396,000			$ 0
Revolving credit facility \| Amended RCF To The End Of March 2022 Through March 2023 \| Line of Credit [Member]
Restructuring Cost and Reserve [Line Items]
Revolving credit facility, maximum borrowing capacity				329,000,000	329,000,000	€ 294,000,000
Revolving credit facility \| Bank Syndicate RCF \| Line of Credit [Member]
Restructuring Cost and Reserve [Line Items]
Revolving credit facility, maximum borrowing capacity				235,200,000	235,200,000	210,000,000.0
Proceeds from lines of credit	$ 156,800,000	€ 140,000,000
Investments [Member]
Restructuring Cost and Reserve [Line Items]
Marketable securities				$ 22,000,000	$ 22,000,000	€ 20,000,000
Interest rate percentage				0.25%	0.25%	0.25%
Closing R&D Operations In Palo Alto
Restructuring Cost and Reserve [Line Items]
Restructuring costs				$ (50,000.00)	$ (497,000)
New Organization Structure
Restructuring Cost and Reserve [Line Items]
Restructuring costs				(400,000)	(1,133,000)
New Organization Structure \| Research and Development expense
Restructuring Cost and Reserve [Line Items]
Restructuring costs				(40,000.00)	(200,000)
New Organization Structure \| Sales and Operations expense
Restructuring Cost and Reserve [Line Items]
Restructuring costs				$ (320,000)	$ (900,000)
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