Warrants - Narrative (Details) - Earnout Warrants	6 Months Ended
	Jun. 30, 2018 day $ / shares € / shares shares
Class of Warrant or Right [Line Items]
Warrants issued (in shares)	3,000,000
Price per share underlying the warrants (in dollars per share) | $ / shares	$ 13
Warrants trading days threshold | day	20
Warrants consecutive trading days threshold | day	30
Warrants expiration term	5 years
Warrants outstanding (in shares)	3,000,000
Ordinary Shares
Class of Warrant or Right [Line Items]
Number of shares entitled to each warrant (in shares)	1
Exercise price (in dollars per share) | € / shares	$ 0.10