Restructuring - Restructuring Reserve (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Beginning balance	$ 0.5	$ 1.5	$ 1.0
Expense	0.6	0.1	3.4
Ending balance	0.0	0.5	1.5
Severance and relocation
Restructuring Reserve [Roll Forward]
Cash expenditures	(1.1)	(1.1)	(0.7)
Other
Restructuring Reserve [Roll Forward]
Cash expenditures	0.0	0.0	(0.1)
Non-cash acceleration of options
Restructuring Reserve [Roll Forward]
Expense			2.1
Non-cash acceleration of options	$ 0.0	$ 0.0	$ (2.1)