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, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Segment Reporting [Abstract]
Earnings from operations for segments	$ 185.8	$ 206.9	$ 685.2	$ 626.8
Unallocated corporate expenses	(59.4)	(42.9)	(163.3)	(128.5)
Interest expense and financing costs	(10.1)	(10.8)	(29.7)	(31.9)
Other expense, net	(1.8)	(2.8)	(5.1)	(7.3)
Earnings from operations before income taxes	$ 114.5	$ 150.4	$ 487.1	$ 459.1