Information about Stock Options Outstanding and Exercisable (Detail) - $ / shares shares in Thousands	9 Months Ended
	Oct. 31, 2015	Jan. 31, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares	3,761	5,569
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 3 months 18 days
Options Outstanding, Weighted-Average Exercise Price	$ 32.44	$ 25.89
Options Exercisable, Number of Shares	2,531
Options Exercisable, Weighted-Average Exercise Price	$ 22.13
$ 9.85 to $18.80
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares	870
Options Outstanding, Weighted-Average Remaining Contractual Life	3 years 10 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 13.28
Options Exercisable, Number of Shares	870
Options Exercisable, Weighted-Average Exercise Price	$ 13.28
$18.84 to $24.75
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares	899
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 9 months 18 days
Options Outstanding, Weighted-Average Exercise Price	$ 19.81
Options Exercisable, Number of Shares	899
Options Exercisable, Weighted-Average Exercise Price	$ 19.81
$30.92 to $36.59
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares	790
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 8 months 12 days
Options Outstanding, Weighted-Average Exercise Price	$ 32.84
Options Exercisable, Number of Shares	616
Options Exercisable, Weighted-Average Exercise Price	$ 32.44
$45.08 to $73.21
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Number of Shares	1,202
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 10 months 24 days
Options Outstanding, Weighted-Average Exercise Price	$ 55.47
Options Exercisable, Number of Shares	146
Options Exercisable, Weighted-Average Exercise Price	$ 45.7