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Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2018	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Income Taxes
Effective tax rate (as a percent)			(8.70%)	130.40%
Net benefit from Tax Cuts and Jobs Acts of 2017				$ 41.7
Benefits from change in uncertain tax positions in US and Canada				36.0
Income tax credits and incentives			$ 12.3	13.7
State income tax expense			$ 7.4
Goodwill impairment charge				$ 33.9
Federal statutory rate (as a percent)			21.00%	24.50%	35.00%
Valuation allowance on foreign tax credits	$ 38.1		$ 38.1
Amount of uncertain tax positions for future years		$ 26.2
Gross book-tax differences from non-U.S. subsidiaries			$ 1,800.0

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