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		6 Months Ended
		Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Segment Reporting [Abstract]
Earnings from operations for segments	[1]	$ 110.9	$ 236.2	$ 86.9	$ 446.0
Unallocated corporate expenses		(43.4)	(51.9)	(96.1)	(100.8)
Interest expense and financing costs		(11.1)	(9.8)	(20.9)	(20.2)
Other income, net		0.8	0.9	26.2	1.9
Other operating expenses		(7.8)	0.0	(36.5)	0.0
Earnings (loss) from operations before income taxes		49.4	$ 175.4	(40.4)	$ 326.9
Merger related expenses		$ 7.8		24.5
Charitable contribution expense				$ 12.0

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