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	9 Months Ended
Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Segment Reporting [Abstract]
Earnings from operations for segments	$ 203.7	$ 192.1	$ 616.6	$ 580.1
Unallocated corporate expenses	(43.4)	(36.9)	(129.3)	(115.4)
Interest and other expenses, net	(9.9)	(9.7)	(28.2)	(34.5)
Earnings from operations before income taxes	$ 150.4	$ 145.5	$ 459.1	$ 430.2

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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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