Income Taxes (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
U.S. federal tax	21.00%		24.50%	35.00%
Tax Cuts And Jobs Act Of 2017 Income Tax Expense Benefit			$ 41.7
Tax Cuts And Jobs Act Of 2017 Transition Tax For Accumulated Foreign Earnings And Future Costs			53.8
Tax Act Additional Federal Portion of the Liability to be Paid in Cash			3.2
Tax Cuts And Jobs Act Of 2017 Change In Tax Rate Deferred Tax Liability Income Tax Expense Benefit			$ 12.1
Tax Cuts and Jobs Act 2017 adjustment to the provisional tax accrual		$ 7.2
Tax Cuts and Jobs Act of 2017 increase to effective tax rate			2.20%
Foreign statutory tax rate, minimum (as percent)			17.00%
Income Tax Holiday [Line Items]
Deferred Tax Liabilities, Net		23.0	$ 23.0	$ 22.4
Accrued income taxes		43.3	43.3	31.4
Cash taxes paid			68.3	42.9	$ 0.0
Tax credit carryforwards		3.1	3.1	0.9
Cumulative undistributed earnings		795.0	795.0
U.S. income and foreign withholding taxes estimate		79.5	79.5
Unrecognized tax benefits		13.5	13.5	15.7	12.9
Unrecognized tax benefits that would impact effective tax rate		13.5	$ 13.5	15.7
Foreign Tax Authority
Income Tax Holiday [Line Items]
Tax benefit of holidays, reduction			50.00%
Net benefit of tax holidays			$ 1.1	$ 8.0	$ 7.1
Loss carryforwards		1.3	1.3
Research Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Income Tax Holiday [Line Items]
Tax Credit Carryforward, Amount		$ 1.7	$ 1.7