Income Taxes - Deferred Tax Assets, Net (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)
Deferred Tax Assets, Net [Abstract]
Foreign earnings repatriated	$ 455.0
Income tax benefits, net, foreign earnings repatriated	3.2
Deferred tax assets, net, benefit, deductible foreign exchange losses on repatriation measured at foreign exchange rate	5.2	$ 5.2
Deferred tax liabilities, net, state income taxes, net of domestic benefit	$ 2.0	2.0
Deferred tax assets, net, increase (decrease), amount, changes in foreign exchange rates		$ (2.9)