Consolidated Comprehensive Income Statements (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Tax effect on translation adjustments	$ (6.6)	$ 32.3
Tax effect on net gain (loss) on derivatives	(5.3)	(10.7)
Tax effect on derivatives reclassification adjustments	1.7	10.6
Tax effect on pension and postretirement benefits reclassification adjustments	$ 11.0	$ 12.9