Segment Information - Reconciliation of Segments' Earnings from Operations to Company's Consolidated Earnings from Operations Before Income Taxes (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2015	Apr. 30, 2014
Segment Reporting [Abstract]
Earnings from operations for segments	$ 206.2	$ 244.1
Unallocated corporate expenses	(36.2)	(34.3)
Interest and other expenses, net	(9.3)	(16.3)
Earnings from operations before income taxes	$ 160.7	$ 193.5