CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income	$ 180.0	$ 253.8	$ 468.4	$ 555.5
Other comprehensive income (loss), net of tax:
Foreign currency translation gain (loss)	21.6	25.4	(265.5)	(14.3)
Derivatives:
Deferred loss on cash flow hedges	(0.7)		(10.1)
Reclassification adjustment of net loss on cash flow hedges included in earnings	1.0		2.2
Defined benefit pension and other postretirement benefit plans:
Amortization and settlement recognition of net actuarial loss, included in pension cost	9.0	4.5	26.2	12.6
Amortization and settlement recognition of prior service cost, included in pension cost	1.0	0.4	2.5	1.3
Other comprehensive income (loss), net of tax	31.9	30.3	(244.7)	(0.4)
Comprehensive income	211.9	284.1	223.7	555.1
Less: Comprehensive income attributable to noncontrolling interests	(1.8)	(1.4)	(3.4)	(3.1)
Comprehensive income attributable to common stockholders	$ 210.1	$ 282.7	$ 220.3	$ 552.0