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, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Segment Reporting [Abstract]
Earnings from operations for segments	$ 169.3	$ 185.8	$ 615.3	$ 685.2
Unallocated corporate expenses	(50.8)	(59.4)	(151.7)	(163.3)
Interest expense and financing costs	(9.2)	(10.1)	(29.4)	(29.7)
Other expense, net	(4.2)	(1.8)	(2.2)	(5.1)
Earnings from operations before income taxes	$ 105.1	$ 114.5	$ 432.0	$ 487.1