Employee and Director Stock Plans - Schedule Of Share-based Compensation Options Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Jan. 31, 2018 USD ($) $ / shares shares
Number of Shares
Options outstanding (in shares) | shares	0.6
Exercised (in shares) | shares	(0.4)
Options outstanding (in shares) | shares	0.2
Options available for grant (in shares) | shares	22.2
Weighted average price per share
Options outstanding, beginning balance (per share) | $ / shares	$ 39.25
Exercised (per share) | $ / shares	38.66
Options outstanding, ending balance (per share) | $ / shares	$ 40.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options outstanding, Weighted average contractual term	2 years 10 months 13 days
Options outstanding, Aggregate Intrinsic Value | $	$ 16.4
Closing stock price (in dollars per share) | $ / shares	$ 115.62