Schedule Of Stock Options Outstanding Expected To Vest And Stock Options Outstanding Exercisable (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Options outstanding expected to vest	8,354
Shares, Options exercisable	21,001
Shares, Total outstanding options vested and expected to vest	29,355
Aggregate Intrinsic Value, Options outstanding expected to vest	$ 81,276
Aggregate Intrinsic Value, Options exercisable	843,971
Aggregate Intrinsic Value, Total outstanding options vested and expected to vest	$ 925,247
Weighted Average Remaining Contract Life, Options outstanding expected to vest, years	9 years
Weighted Average Remaining Contract Life, Options exercisable, years	5 years 3 months 18 days
Weighted Average Remaining Contract Life, Total outstanding options vested and expected to vest, years	6 years 3 months 18 days
WAEP, Options outstanding expected to vest	$ 56.21
WAEP, Options exercisable	$ 25.75
WAEP, Total outstanding options vested and expected to vest	$ 34.42