Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%
Effective income tax rate (as a percent)	7.80%	21.80%
Income tax expense	$ 4.7	$ 5.2
Income tax expense (benefit), tax credit, discrete items	(10.3)	(2.8)
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	3.3
Other Tax Expense (Benefit)	(6.5)
Gross unrecognized tax benefits, excluding income tax penalties and interest	37.3			$ 37.2
Net unrecognized tax benefits, excluding interest and penalties that would affect the Company's net income if recognized	21.1
Interest and penalties benefit (cost)	0.3	0.4
Accruals for payment of interest and penalties	10.2
Estimated reduction in unrecognized tax benefits due to tax audit resolutions during the next twelve months	3.0
State and Local Jurisdiction [Member]
Valuation allowance, deferred tax asset, increase (decrease), amount		(2.1)
Domestic Tax Authority [Member]
Valuation allowance, deferred tax asset, increase (decrease), amount		$ (0.7)
Tax Reform [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%
Deferred Federal Income Tax Expense (Benefit)	23.9
Current Foreign Income Tax Expense (Benefit)	$ (17.4)