Income Taxes - Components of Deferred Income Tax assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets:
Other long-term liabilities	$ 127.0	$ 126.0
Losses and credits	34.8	27.9
Accrued warranty	15.8	14.5
Other current liabilities	17.7	15.0
Payroll-related obligations	18.5	23.4
Other	6.0	9.4
Gross deferred tax assets	219.8	216.2
Less valuation allowance	(17.4)	(1.1)
Deferred tax assets, net	202.4	215.1
Deferred tax liabilities:
Intangible assets	(42.2)	(40.0)
Property, plant and equipment	(55.9)	(50.5)
Inventories	(18.6)	(14.1)
Other	(7.1)	(2.6)
Deferred tax liabilities	(123.8)	(107.2)
Deferred tax assets, net of deferred tax liabilities	$ 78.6	$ 107.9