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Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Taxes
Effective tax rate (as a percent)			130.40%	(6.20%)
Net benefit from Tax Cuts and Jobs Acts of 2017			$ 41.7
Benefit from change in uncertain tax positions in US and Canada			36.0
Benefit from income tax credits and incentives			13.7
Amount of goodwill which was non-deductible for tax purposes	$ 33.9		$ 33.9
Amount of uncertain tax positions for future years	$ 26.2
Federal statutory rate (as a percent)					21.00%		35.00%
Blended statutory rate (as a percentage)						24.50%
Provisional amount related to remeasurement of deferred tax balance		$ 36.1
Provisional amount of tax benefit related to releasing of deferred tax liability		77.0
Provisional amount of income tax expense related to transition tax on foreign subsidiaries		$ 71.4
Gross book-tax differences from non-U.S. subsidiaries							$ 1,700.0

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Percentage of domestic federal statutory blended tax rate applicable to pretax income (loss).

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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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