Income Taxes (Narrative) (Details) $ in Millions	9 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2017 EUR (€)	Sep. 30, 2014 USD ($)
Income Taxes [Line Items]
Cash paid for taxes (net of cash refunds)		$ 1,348.8	$ 440.8	$ 392.9
U.S. federal statutory tax rate		35.00%	35.00%	35.00%
Percentage of the undistributed earnings in countries with a statutory tax rate of 24% or higher		80.00%			80.00%
Statutory tax rate percentage or higher		24.00%			24.00%
Income tax benefit on tax losses from foreign holding company		$ 111.4
Goodwill impairment charge	$ 145.3	145.3
Goodwill impairment charge deductible for tax purposes		0.0
Excess tax benefits recognized under new accounting standard		17.6
Business separation additional income tax expense			$ 51.8
Foreign earnings repatriated			443.8
Deferred tax assets, valuation allowance		107.7	165.1
Debt instrument, face amount		317.2			€ 300,000,000
Cumulative undistributed earnings		6,032.5
US Income and foreign withholding taxes estimate		1,443.9
Unrecognized tax benefits		146.4	90.2	$ 83.8		$ 93.1
Unrecognized tax benefits that would impact effective tax rate		73.8	46.5
Interest and penalties related to unrecognized tax benefits		3.7	1.8	$ (1.9)
Accrued interest and penalties		12.1	$ 8.4
Federal
Income Taxes [Line Items]
Tax credit carryforwards		53.9
State
Income Taxes [Line Items]
Tax credit carryforwards		1.2
Operating loss carryforwards		75.2
Foreign
Income Taxes [Line Items]
Tax credit carryforwards		21.0
Operating loss carryforwards		247.3
Unused carryforwards and credits that have an expiration period		221.7
Deferred tax assets operating loss carryforwards, foreign		52.4
Energy-from-Waste (EfW)
Income Taxes [Line Items]
Deferred tax assets capital loss carryforwards		$ 49.1