Income Taxes - Effective Tax Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Tax Rate Reconciliation
Income tax expense at U.S. statutory rate	$ 14.1	$ 3.6	$ 7.9
State income taxes, net of federal tax benefit	1.7	0.2	0.4
Foreign income, net of credit on foreign taxes	0.7	8.5	0.0
Effective tax rate differential of earnings outside of U.S.	2.6	(0.3)	0.5
Change in valuation allowance	38.4	7.6	6.8
Research & experimentation credits	(0.9)	(0.5)	(0.7)
Non-deductible items	0.4	0.7	0.7
Change in uncertain tax positions	0.2	0.1	(0.2)
Share-based compensation	(3.3)	0.0	0.0
Domestic production activities deduction	0.0	(0.4)	(1.2)
Tax effect of insurance proceeds	0.0	0.0	(6.0)
Effective Income Tax Rate Reconciliation, Capital Loss Carryover, Amount	(29.7)	0.0	0.0
Tax effect of 2017 tax reform federal rate change	(11.3)	(26.7)	0.0
Tax effect of carryforward foreign tax credits	(0.6)	(9.4)	0.0
Other items	1.1	0.0	2.4
Income tax expense (benefit), net	$ 13.4	$ (16.6)	$ 10.6