Income Taxes - Effective Tax Rate-Shareholder Activism-Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Legal, executive separation, and other professional service fees in connection with response to proxy contest	$ 31.4	$ 0.0	$ 61.3	$ 0.0
Net tax benefit related to legal, executive separation, and other professional service fees in connection with response to proxy contest			$ 8.4