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
Apr. 30, 2016	Apr. 30, 2015
Segment Reporting [Abstract]
Earnings from operations for segments	$ 175.2	$ 206.2
Unallocated corporate expenses	(40.6)	(36.2)
Interest and other expenses, net	(11.5)	(9.3)
Earnings from operations before income taxes	$ 123.1	$ 160.7

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration