Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 261.4	$ 198.6	$ 687.7	$ 189.6
Other comprehensive income (loss), net of tax:
Pension and other postretirement benefit plan adjustments (net of tax (expense) of ($4.2), ($7.2), ($12.8) and ($22.0))	14.1	20.2	42.1	60.6
Currency translation adjustments	(2.7)	(95.7)	(12.2)	(35.3)
Net change in unrealized gains and losses on cash flow hedges (net of tax benefit (expense) of $0.7, ($6.0), $6.7 and ($5.4))	(1.9)	16.4	(20.2)	15.9
Net change in unrealized gains and losses on available-for-sale investments (net of tax (expense) benefit of ($0.1), ($0.1), ($0.4) and $0.5)	0.6	0.1	2.0	(2.5)
Other comprehensive income (loss)	10.1	(59.0)	11.7	38.7
Comprehensive income	$ 271.5	$ 139.6	$ 699.4	$ 228.3