Condensed Consolidated Statement of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 198.6	$ 216.9	$ 189.6	$ 621.1
Other comprehensive (loss) income, net of tax:
Pension and other postretirement benefit plan adjustments (net of tax expense of $7.2, $12.6, $22.0 and $37.8)	20.2	23.8	60.6	72.1
Currency translation adjustments	(95.7)	24.9	(35.3)	(0.5)
Net change in unrealized gains and losses on cash flow hedges (net of tax expense (benefit) of $6.0, ($1.0), $5.4 and $2.3)	16.4	(4.4)	15.9	3.6
Net change in unrealized gains and losses on available-for-sale investments (net of tax expense (benefit) of $0.1, ($0.0), ($0.5) and ($0.0))	0.1	0.0	(2.5)	(0.1)
Other comprehensive (loss) income	(59.0)	44.3	38.7	75.1
Comprehensive income	$ 139.6	$ 261.2	$ 228.3	$ 696.2