Share-Based Compensation - Breakdown of Closing Balance of Non-Employee Warrants (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares	Dec. 31, 2016 € / shares shares	Dec. 31, 2015 € / shares shares	Dec. 31, 2014 € / shares shares	Dec. 31, 2013 shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, weighted-average exercise price, options (in Euro per share) | € / shares				€ 23.92	€ 20.97	€ 14.10
Exercisable, weighted-average exercise price, options (in Euro per share) | € / shares				€ 17.73	€ 11.85	€ 5.81
Weighted-average remaining contractual life, options (in years)	6 years 10 months 24 days	7 years 10 months 24 days	8 years 2 months 12 days
BSA
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number outstanding, options (in shares) | shares	188,125	154,910	199,408	188,125	154,910	199,408	542,148
Outstanding, weighted-average exercise price, options (in Euro per share) | $ / shares	$ 19.04	$ 15.72	$ 7.54
Number of exercisable options (in shares) | shares	117,096	117,783	155,609	117,096	117,783	155,609
Exercisable, weighted-average exercise price, options (in Euro per share) | $ / shares	$ 11.73	$ 8.49	$ 6.88
Weighted-average remaining contractual life, options (in years)	7 years 3 months 18 days	7 years 4 months 24 days	7 years 6 months