v3.10.0.1
Share-based Compensation - Summary of Stock Options and Changes (Management Equity Stock Option Plan) (Detail) - Management Equity Stock Option Plan [Member]
12 Months Ended
Dec. 31, 2018
€ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Stock options, Outstanding at January 1, 2018 | shares 231,924
Stock options, Granted | shares 0
Stock options, Exercised | shares 231,924
Stock options, Forfeited | shares 0
Stock options, Expired | shares 0
Stock options, Outstanding at December 31, 2018 | shares 0
Weighted average exercise price, Outstanding at January 1, 2018 | € / shares € 35.72
Weighted average exercise price, Granted | € / shares 0
Weighted average exercise price, Exercised | € / shares 35.72
Weighted average exercise price, Forfeited | € / shares 0
Weighted average exercise price, Expired | € / shares 0
Weighted average exercise price, Outstanding at December 31, 2018 | € / shares € 0