Segment Information - Reconciliation of Segments' Earnings from Operations to Company's Consolidated Earnings from Operations Before Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Segment Reporting [Abstract]
Earnings from operations for segments	$ 212.8	$ 222.5	$ 388.0	$ 428.7
Unallocated corporate expenses	(37.9)	(40.1)	(78.5)	(76.3)
Interest and other expenses, net	(13.4)	(13.6)	(24.8)	(22.9)
Other Operating Expense	0.0	(9.6)	0.0	(9.6)
Earnings from operations before income taxes	$ 161.5	$ 159.2	$ 284.7	$ 319.9