Basis of Presentation (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Jan. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Leases
Decrease to retained earnings				$ (5.1)
Right-of-use assets	$ 8.2	$ 4.7		$ 4.7
Other non-current assets		us-gaap:OtherAssetsNoncurrent		us-gaap:OtherAssetsNoncurrent
Current lease liabilities	4.1	$ 1.9		$ 1.9
Other current liabilities		us-gaap:OtherLiabilitiesCurrent		us-gaap:OtherLiabilitiesCurrent
Non-current lease liabilities	4.1	$ 2.8		$ 2.8
Other non-current liabilities		us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Total operating lease liabilities	8.2	$ 4.7		$ 4.7
Operating lease expense		1.2	$ 1.0	$ 3.9	$ 3.2
Broader collaboration arrangement
Leases
Reclassification from Property, plant and equipment to other noncurrent assets		$ 23.1
ASU 2016-02
Leases
Decrease to retained earnings	$ (5.1)
Weighted-average remaining lease term	3 years
Weighted-average discount rate	4.90%