Stock-based Compensation - Stock Option Activities (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 30, 2021 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding | shares	719,143
Shares, Granted | shares	13,100
Shares, Exercised | shares	(77,403)
Shares, Forfeited | shares	(3,131)
Shares, Expired | shares	0
Shares, Outstanding | shares	651,709
Shares, Exercisable | shares	531,761
Weighted-Average Exercise Price, Outstanding	$ 38.33
Weighted-Average Exercise Price, Granted	111.51
Weighted-Average Exercise Price, Exercised	27.77
Weighted-Average Exercise Price, Forfeited	55.43
Weighted-Average Exercise Price, Expired	0
Weighted-Average Exercise Price, Outstanding	40.98
Weighted-Average Exercise Price, Exercisable	36.80
Weighted-Average Grant-date Fair Value, Granted	$ 51.10
Total Intrinsic Value Of Options Exercised | $	$ 6,363
Weighted-Average Remaining Contractual Term, Outstanding	4 years 5 months 15 days
Weighted-Average Remaining Contractual Term, Exercisable	3 years 6 months 21 days
Aggregate Intrinsic Value, Outstanding | $	$ 37,040
Aggregate Intrinsic Value, Exercisable | $	$ 32,298