Segment Information - Reconciliation of Segments' Earnings from Operations to Company's Consolidated Earnings from Operations Before Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Segment Reporting [Abstract]
Earnings from operations for segments	[1]	$ 234.0	$ 169.3	$ 320.9	$ 615.3
Unallocated corporate expenses		(50.6)	(50.8)	(146.7)	(151.7)
Interest expense and financing costs		(10.7)	(9.2)	(31.6)	(29.4)
Other expense (income), net		(5.7)	(4.2)	20.6	(2.2)
Other operating expenses		(18.4)	0.0	(55.0)	0.0
Earnings from operations before income taxes		$ 148.6	$ 105.1	108.2	$ 432.0
Merger related expenses				43.0
Charitable contribution expense				$ 12.0

[1] Represents earnings (loss) from operations before (i) unallocated corporate expenses, (ii) Interest expense and financing costs, (iii) Other expense (income), net and (iv) other operating expenses.