Share-Based Payments - Founders' Program 2007 (Details) - Founder's Program 2007	1 Months Ended		24 Months Ended
	Feb. 29, 2008 shares	Nov. 30, 2007 shares	Feb. 28, 2010 $ / shares shares	Mar. 31, 2017 € / shares shares
Share-Based Payments
Outstanding				623
Outstanding options exercise price (in dollars per share) | € / shares				€ 1.00
Percentage that vests during the period	25.00%	25.00%	50.00%
Vested (in shares)	155	156
Monthly vesting percentage			2.083%
Shares vested monthly (in shares)			13
Weighted-average grant date fair value (in dollars per share) | $ / shares			$ 144.23