Tax benefit from calculation of total foreign earnings and profits of foreign subsidiaries.

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Amount of current foreign income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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

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The amount the liability recorded for the income tax examination increased or decreased in the current year/accounting period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of reasonable estimate for income tax expense (benefit) for which accounting for tax effect for remeasurement of deferred tax from change in tax rate is incomplete pursuant to Tax Cuts and Jobs Act.

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Amount of reasonable estimate for undistributed accumulated earnings of foreign subsidiary subject to transition tax for which accounting is incomplete pursuant to Tax Cuts and Jobs Act.

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Amount of reasonable estimate for income tax expense for which accounting for tax effect from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated is incomplete pursuant to Tax Cuts and Jobs Act.

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Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Income Taxes - Additional information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income taxes
Valuation allowance		$ 169.1	$ 197.1
Federal corporate tax rate (as a percent)		21.00%	24.50%	35.00%
Provisional income tax (benefit)			$ (32.0)
Undistributed earnings from foreign subsidiaries			79.8
One-time transition tax on accumulated foreign earnings			64.0
Tax benefit from foreign earnings and profits		$ (1.5)
Tax benefit from income tax examination			27.7
Tax benefit from income tax examination, R&D credits	$ 26.2
Tax benefit from foreign subsidiaries		(43.2)	(47.1)	$ (29.3)
Change in valuation allowance		28.0
Amount of uncertain tax positions for future years	$ 26.2
United States
Income taxes
Valuation allowance			38.1
Tax benefit from income tax examination		(38.1)
Canada
Income taxes
Valuation allowance		$ 6.0
Change in valuation allowance			$ 13.1