Income Taxes - Additional information regarding Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Valuation Allowance		$ 2.1	$ 2.1	$ 10.4
Foreign Earnings Reinvested, Income taxes on Undistributed Earnings		$ 41.8	$ 41.8
U.S. federal tax rate	35.00%	21.00%	24.50%	35.00%	35.00%
Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit)			$ (30.2)
Tax Cuts and Jobs Act, Incomplete Accounting, Transition Tax for Accumulated Foreign Earnings, Provisional Income Tax Expense			19.5
Discrete tax benefits			$ 21.7	$ 20.1	$ 7.5
Income Tax Expense (Benefit), Discrete Items, Percentage of Pre-Tax Income			3.60%	4.90%	2.40%
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		$ 36.3	$ 36.3
Tax Credit Carryforwards, Foreign Expiration Period, Minimum			7 years
Deferred Tax Assets, Operating Loss Carryforwards		9.4	$ 9.4
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards		227.5	227.5
Tax Credit Carryforward, Amount		22.9	22.9
Deferred Tax Assets, Tax Credit Carryforwards		14.9	14.9
Deferred Tax Assets, Operating Loss Carryforwards		9.2	9.2
Operating Loss Carryforwards, Valuation Allowance		$ 2.1	$ 2.1