Employee Benefits and Stock-based Compensation - Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding	1,124,646	1,459,064	1,611,344
Shares, Granted	51,200	66,850	116,600
Shares, Exercised	(421,736)	(366,886)	(232,205)
Shares, Forfeited	(11,618)	(14,931)	(20,974)
Shares, Expired	(23,349)	(19,451)	(15,701)
Shares, Outstanding	719,143	1,124,646	1,459,064
Shares, Exercisable	592,729
Weighted-Average Exercise Price, Outstanding	$ 32.93	$ 28.31	$ 24.56
Weighted-Average Exercise Price, Granted	59.54	50.56	42.73
Weighted-Average Exercise Price, Exercised	24.52	15.52	5.54
Weighted-Average Exercise Price, Forfeited	46.69	46.29	53.50
Weighted-Average Exercise Price, Expired	70.11	64.53	54.35
Weighted-Average Exercise Price, Outstanding	38.33	32.93	28.31
Weighted-Average Exercise Price, Exercisable	35.27
Weighted-Average Grant-date Fair Value, Granted	$ 28.37	$ 25.35	$ 21.75
Total Intrinsic Value of options Exercised	$ 19,401	$ 13,263	$ 8,867
Weighted-Average Remaining Contractual Term, Outstanding	4 years 5 months 1 day
Weighted-Average Remaining Contractual Term, Exercisable	3 years 6 months 21 days
Aggregate Intrinsic Value, Outstanding	$ 40,358
Aggregate Intrinsic Value, Exercisable	$ 35,092