CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Consolidated net income	$ 148.9	$ 161.9	$ 288.4	$ 301.7
Other comprehensive (loss) income, net of tax:
Foreign currency translation (loss) gain	(387.5)	25.2	(287.1)	(39.7)
Derivatives:
Deferred loss on cash flow hedges	(8.9)		(9.4)
Reclassification adjustment of net loss on cash flow hedges included in earnings	2.5		1.2
Defined benefit pension and other postretirement benefit plans:
Amortization and settlement recognition of net actuarial loss, included in pension cost	8.5	3.2	17.2	8.1
Amortization and settlement recognition of prior service cost, included in pension cost	1.0	0.4	1.5	0.9
Other comprehensive (loss) income, net of tax	(384.4)	28.8	(276.6)	(30.7)
Comprehensive (loss) income	(235.5)	190.7	11.8	271.0
Less: Comprehensive income attributable to noncontrolling interests	(0.5)	(1.0)	(1.6)	(1.7)
Comprehensive (loss) income attributable to common stockholders	$ (236.0)	$ 189.7	$ 10.2	$ 269.3