v3.10.0.1
Summary of Significant Accounting Policies - Additional Information (Details) - EUR (€)
€ in Millions
 12 Months Ended
Jan. 01, 2019
Dec. 31, 2018
Disclosure of summary of significant accounting policies [line items]    
Term of financial liability settlement   12 months
Maturity of cash and cash equivalent   three months or less
Periods of maturity for highly liquid investments   three months or less
Material modifications to any share-based payment transactions   There were no material modifications to any share-based payment transactions during 2018, 2017, and 2016
Adoption of New Accounting Standards    
Disclosure of summary of significant accounting policies [line items]    
Increase in assets and liabilities € 500  
Top of range    
Disclosure of summary of significant accounting policies [line items]    
Average duration of investment portfolio   1 year
Acquired Developed Technology and Patents    
Disclosure of summary of significant accounting policies [line items]    
Estimated useful lives   2 to 5 years
Property and Equipment    
Disclosure of summary of significant accounting policies [line items]    
Estimated useful lives   3 to 5
Leasehold Improvements    
Disclosure of summary of significant accounting policies [line items]    
Estimated useful lives   shorter of the lease term or useful life