Income Taxes - Additional Disclosures (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Operating Loss Carryforwards [Line Items]
Increase (decrease) to the valuation allowance	$ 0.6
Undistributed losses of foreign subsidiaries	70.0
Undistributed earnings of foreign subsidiaries, estimated taxes recognized upon distribution	3.8
Amount of foreign uncertain tax positions to expire within twelve months	2.2
Income tax penalties and interest expense	0.3	$ 1.2	$ 0.2
Accrued interest and penalties	1.8	$ 1.5	$ 0.3
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforward	100.6
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforward	56.9
Tax credit carryforward	$ 1.7