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, 2020 USD ($) $ / shares shares
Number of Shares
Options outstanding (in shares) | shares	0.8
Granted (in shares) | shares	0.0
Exercised (in shares) | shares	(0.3)
Canceled/Forfeited (in shares) | shares	(0.1)
Options outstanding (in shares) | shares	0.4
Weighted average exercise price per share
Options outstanding, beginning balance (in dollars per share) | $ / shares	$ 23.95
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	23.43
Canceled/Forfeited (in dollars per share) | $ / shares	21.27
Options outstanding, ending balance (in dollars per share) | $ / shares	$ 24.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Options vested and exercisable at January 31, 2020 (in shares) | shares	0.2
Shares available for grant at January 31, 2020 (in shares) | shares	14.6
Options vested and exercisable at January 31, 2020, Weighted average exercise price per share (in dollars per share) | $ / shares	$ 31.73
Options vested, exercisable and outstanding, Weighted average remaining contractual term (in years)	6 years 7 months 6 days
Options vested and exercisable at January 31, 2020, Weighted average remaining contractual term (in years)	3 years 10 months 24 days
Options vested, exercisable and outstanding at January 31, 2020, Aggregate Intrinsic Value | $	$ 73.8
Options vested and exercisable at January 31, 2020, Aggregate Intrinsic Value | $	$ 25.3
Closing stock price (in dollars per share) | $ / shares	$ 196.85