Divestment - Narrative (Details) € in Millions, $ in Millions				3 Months Ended		6 Months Ended
	Jan. 02, 2020 USD ($)	Jan. 02, 2020 EUR (€)	Dec. 27, 2019 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Write-off of deferred financing fees			$ 5.7
Interest expense				$ 39.1	$ 47.2	$ 86.4	$ 94.0
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Pre-tax costs					0.6		1.7
Allocated pre-tax interest expense						$ 5.0
Total proceeds anticipated		€ 180.0			6.9		6.9
Disposal Group, Disposed of by Sale, Not Discontinued Operations | VARTAAG
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total proceeds anticipated	$ 323.1
Pre-tax loss					$ 137.6		$ 137.6