Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total Other items, net	$ 0.0	$ 16.9
Interest expense	(51.0)	(48.2)
Earnings before income taxes	58.7	90.0
Income tax provision	(12.9)	(19.2)
Net earnings	46.1	70.8
Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net earnings	2.3	1.0
Gains and losses on cash flow hedges | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total Other items, net	1.9	2.8
Interest expense	(0.5)	(0.1)
Earnings before income taxes	1.1	2.7
Income tax provision	(0.2)	(0.6)
Net earnings	0.9	2.1
Amortization of defined benefit pension items | Amount Reclassified from AOCI
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Actuarial gain/(loss)	1.9	(1.3)
Earnings before income taxes	1.9	(1.3)
Income tax provision	(0.5)	0.2
Net earnings	$ 1.4	$ (1.1)