Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%		35.00%
Weighted Average Deferred Income Tax Provision Rate	25.00%			39.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount		$ 0.0	$ 0.0	$ (42.5)
Transition Tax Expense					$ 7.5
Effective Income Tax Rate Reconciliation, Federal Transition Tax, Amount		0.0	(0.6)	7.5
Unrecognized Tax Benefits, Interest on Income Taxes Accrued		0.4	0.3
Income tax expense (benefit)		22.1	18.3	(9.9)
Deferred Tax Assets, Tax Credit Carryforwards, Foreign			4.5
Unrecognized Tax Benefits		$ 4.5	$ 3.3	$ 3.3