v3.10.0.1
Business Combinations - Additional Information (Details)
€ in Millions
12 Months Ended
Dec. 31, 2018
shares
Dec. 31, 2017
EUR (€)
shares
Business
Dec. 31, 2016
shares
Restricted Stock Awards      
Disclosure of detailed information about business combination [line items]      
Share-based payment transactions | shares 0 61,880 0
Acquisitions in 2017      
Disclosure of detailed information about business combination [line items]      
Number of business acquired | Business   5  
Total purchase consideration   € 85  
Cash paid for business acquisition   52  
Issue of equity for business acquisition   33  
Goodwill   71  
Acquired intangible assets   17  
Deferred tax liabilities   4  
Tangible assets   1  
Acquisitions in 2017 | Arrangement One      
Disclosure of detailed information about business combination [line items]      
Business combination, compensation expenses   € 6  
Acquisitions in 2017 | Arrangement One | Restricted Stock Awards      
Disclosure of detailed information about business combination [line items]      
Share-based payment transactions | shares   61,880  
Acquisitions in 2017 | Top of range      
Disclosure of detailed information about business combination [line items]      
Business combination, compensation expenses   € 22  
Business combination, compensation expenses service period   3 years  
Acquisitions in 2017 | Top of range | Arrangement One      
Disclosure of detailed information about business combination [line items]      
Business combination, compensation expenses service period   3 years  
Acquisitions in 2017 | Bottom Of Range [Member] | Arrangement One      
Disclosure of detailed information about business combination [line items]      
Business combination, compensation expenses service period   2 years