Options Granted under Stock Option Plans (Detail) shares in Thousands	9 Months Ended
	Oct. 31, 2015 $ / shares shares
Number of Shares
Options outstanding at the beginning of the year	5,569
Granted	694
Exercised	(2,447)
Expired or cancelled	(55)
Options outstanding at end of year	3,761
Options exercisable at end of year	2,531
Options vested and expected to vest	3,720
Options available for future grant at end of year	13,037
Weighted-Average Term
Options outstanding at end of year	6 years 3 months 18 days
Options exercisable at end of year	5 years 1 month 6 days
Options vested and expected to vest	6 years 3 months 18 days
Weighted-Average Exercise Price
Options outstanding at the beginning of the year | $ / shares	$ 25.89
Granted | $ / shares	62.29
Exercised | $ / shares	25.64
Expired or cancelled | $ / shares	48.68
Options outstanding at end of year | $ / shares	32.44
Options exercisable at end of year | $ / shares	22.13
Options vested and expected to vest | $ / shares	$ 32.17