Business Segment Information (Reconciliation of Operating Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Operating income (loss)	$ (2,328.0)	$ 637.2	$ (1,684.4)	$ 1,304.1
Business and asset actions	(2,927.9)	(57.0)	(2,927.9)	(57.0)
Shareholder activism costs	(31.4)	0.0	(61.3)	0.0
Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	631.3	694.2	1,304.8	1,361.1
Segment Reconciling Items
Segment Reporting Information [Line Items]
Business and asset actions	(2,927.9)	(57.0)	(2,927.9)	(57.0)
Shareholder activism costs	$ (31.4)	$ 0.0	$ (61.3)	$ 0.0