Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 695.8	$ 535.5	$ 825.7
Other comprehensive (loss) income:
Pension and other postretirement benefit plan adjustments (net of tax benefit (expense) of $150.0, ($87.2) and ($159.3))	(475.6)	268.9	312.8
Currency translation adjustments	(55.3)	(48.3)	57.2
Net change in cash flow hedges (net of tax benefit (expense) of $5.5, ($6.6) and $2.8)	(17.4)	18.8	(10.3)
Net change in available-for-sale investments	2.2	(2.1)	(0.1)
Other comprehensive (loss) income	(546.1)	237.3	359.6
Comprehensive income	$ 149.7	$ 772.8	$ 1,185.3