Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2016
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate								24.50%
Undistributed Earnings of Foreign Subsidiaries	$ 378.8			$ 378.8		$ 354.7		$ 354.7
Foreign Earnings Repatriated				13.0
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent					0.60%
Operating Loss Carryforwards	9.4			9.4
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	5.7			5.7
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	6.5			6.5
Deferred Tax Assets, Valuation Allowance	3.5			3.5					$ 3.6
Income Tax Expense (Benefit)	$ 7.5	$ 6.8		$ 13.7	$ 32.3
Effective Income Tax Rate Reconciliation, Percent	24.00%	23.00%		25.00%	67.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount							$ 20.1
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent							42.00%
Deferred Income Tax Expense (Benefit)			$ 8.9			$ 0.3
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount		$ 0.7	$ 12.0