Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Other	$ 0.2				$ 0.4				$ 0.2	$ 0.4
Income tax expense	6.9	$ 5.3	$ 7.5	$ 6.2	4.8	$ 8.9	$ 6.8	$ 25.5	25.9	46.0	$ 8.8
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized (Gain) Loss Arising During Period, Tax									(0.2)	0.1	1.0
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation									0.0	0.0	0.1
Other Comprehensive Income (Loss), Tax									25.7	46.1	9.9
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense									0.0
Operating Loss Carryforwards	7.1				9.4				7.1	9.4
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	1.1				0.0				1.1	0.0	$ 21.9
Deferred Tax Assets, Net of Valuation Allowance, Operating Loss Carryforwards, State and Local	5.6								5.6
Deferred Tax Assets, Valuation Allowance	8.5				3.5				8.5	3.5
Valuation Allowance, Deferred Tax Asset, Change in Amount									5.0
Undistributed Earnings of Foreign Subsidiaries	$ 383.5				$ 354.7				$ 383.5	$ 354.7