Employee Benefits and Stock-based Compensation - Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding	1,459,064	1,611,344	1,703,524
Shares, Granted	66,850	116,600	132,250
Shares, Exercised	(366,886)	(232,205)	(175,187)
Shares, Forfeited	(14,931)	(20,974)	(27,721)
Shares, Expired	(19,451)	(15,701)	(21,522)
Shares, Outstanding	1,124,646	1,459,064	1,611,344
Shares, Exercisable	960,567
Weighted-Average Exercise Price, Outstanding	$ 28.31	$ 24.56	$ 21.66
Weighted-Average Exercise Price, Granted	50.56	42.73	54.66
Weighted-Average Exercise Price, Exercised	15.52	5.54	12.50
Weighted-Average Exercise Price, Forfeited	46.29	53.50	56.97
Weighted-Average Exercise Price, Expired	64.53	54.35	36.31
Weighted-Average Exercise Price, Outstanding	32.93	28.31	24.56
Weighted-Average Exercise Price, Exercisable	30.24
Weighted-Average Grant-date Fair Value, Granted	$ 25.35	$ 21.75	$ 28.28
Total Intrinsic Value of options Exercised	$ 13,263	$ 8,867	$ 7,446
Weighted-Average Remaining Contractual Term, Outstanding	4 years 4 months 6 days
Weighted-Average Remaining Contractual Term, Exercisable	3 years 7 months 24 days
Aggregate Intrinsic Value, Outstanding	$ 31,295
Aggregate Intrinsic Value, Exercisable	$ 29,573