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, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Segment Reporting [Abstract]
Earnings from operations for segments	$ 236.2	$ 249.8	$ 446.0	$ 499.3
Unallocated corporate expenses	(51.9)	(58.6)	(100.8)	(103.8)
Interest expense and financing costs	(9.8)	(9.7)	(20.2)	(19.6)
Other income (expense), net	0.9	0.5	1.9	(3.4)
Earnings from operations before income taxes	$ 175.4	$ 182.0	$ 326.9	$ 372.5