Basis of Preparation - Narratives (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) facility	Mar. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle
Current Fiscal Year End Date	--12-31
Right of use assets	$ 29.8
Operating lease liability	33.1
Operating lease liability, current	$ 7.1
Weighted average lease term	7 years 2 months 12 days
Operating lease weighted average discount rate (percent)	4.70%
Operating lease rental expense	$ 2.0	$ 2.5
Number of leased facililities (facility) | facility	11
ASUe 2016-02
New Accounting Pronouncements or Change in Accounting Principle
Right of use assets			$ 34.8
Operating lease liability			$ 34.8