Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Plan Disclosure [Line Items]
Expenses related to defined contribution plans	$ 6.4	$ 5.5	$ 3.4
Ireland
Defined Contribution Plan Disclosure [Line Items]
Expenses related to defined contribution plans	$ 1.2	1.0	0.8
Defined contribution plans, employer matching percentage of employee's eligible contributions (as a percent)	8.00%
United States
Defined Contribution Plan Disclosure [Line Items]
Expenses related to defined contribution plans	$ 4.2	3.7	1.9
United Kingdom
Defined Contribution Plan Disclosure [Line Items]
Expenses related to defined contribution plans	$ 0.8	0.7	$ 0.6
Defined contribution plans, employer matching percentage of employee's eligible contributions (as a percent)	12.00%
France
Defined Contribution Plan Disclosure [Line Items]
Accrued retirement liability	$ 0.4	0.3
Italy
Defined Contribution Plan Disclosure [Line Items]
Accrued retirement liability	$ 0.3	$ 0.3