Income Taxes - Narrative (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) employee	Dec. 31, 2017 USD ($)	Dec. 31, 1986 USD ($)
Investments, Owned, Federal Income Tax Note [Line Items]
Net operating loss carryforwards		$ 4.8
Research and development credit carryforwards		11.0	$ 3.4
Undistributed earnings of domestic subsidiaries			255.7	$ 23.9
Undistributed earnings of foreign subsidiaries		32.7
Allowance for distributions out of current year GAAP		25.3
Provisional tax obligation			7.7
Adjustment to income tax expense			7.7
Measurement-period adjustment to transition tax obligation		0.2
Adjustment to income tax expense		0.2
Total transition tax obligation		7.9
Adjustment to income tax expense		$ 7.9
Number of highest paid employees | employee		3
Reduction in U.S. Federal corporate rate			7.0
Adjustment to deferred tax expense			$ 7.0
Discrete tax benefit	$ 1.5
Decrease to net deferred tax assets		$ 5.5
Adjustment to deferred income tax expense		5.5
Foreign Tax Authority
Investments, Owned, Federal Income Tax Note [Line Items]
Net operating loss carryforwards, not subject to expiration		10.4
Net operating loss carryforwards, subject to expiration		22.9
Domestic Tax Authority
Investments, Owned, Federal Income Tax Note [Line Items]
Research and development credit carryforwards		2.7
SWITZERLAND | Foreign Tax Authority
Investments, Owned, Federal Income Tax Note [Line Items]
Net operating loss carryforwards, subject to expiration		$ 21.5