Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Other	$ 0.4				$ 0.0				$ 0.4	$ 0.0
Income tax expense	4.8	$ 8.9	$ 6.8	$ 25.5	1.1	$ 2.3	$ 3.3	$ 2.1	46.0	8.8	$ 18.0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized (Gain) Loss Arising During Period, Tax									0.1	1.0	0.2
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation									0.0	0.1	0.8
Other Comprehensive Income (Loss), Tax									46.1	9.9	17.4
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense									0.0
Operating Loss Carryforwards	9.4				30.1				9.4	30.1
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	0.0				21.9				0.0	21.9
Deferred Tax Assets, Net of Valuation Allowance, Operating Loss Carryforwards, State and Local	5.7								5.7
Deferred Tax Assets, Valuation Allowance	3.5				$ 4.0				3.5	4.0
Valuation Allowance, Deferred Tax Asset, Change in Amount									0.5
Income (Loss) from Continuing Operations before Income Taxes, Domestic									(3.7)	$ (20.5)	$ (9.7)
Deferred Tax Liabilities, Gross	5.0								5.0
Undistributed Earnings of Foreign Subsidiaries	354.7								354.7
UNITED STATES
Operating Loss Carryforwards [Line Items]
Deferred Tax Liabilities, Other	$ 2.5								$ 2.5