Employee Benefits and Stock-based Compensation - Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding	1,611,344	1,703,524	1,853,390
Shares, Granted	116,600	132,250	110,500
Shares, Exercised	(232,205)	(175,187)	(235,923)
Shares, Forfeited	(20,974)	(27,721)	(16,708)
Shares, Expired	(15,701)	(21,522)	(7,735)
Shares, Outstanding	1,459,064	1,611,344	1,703,524
Shares, Exercisable	1,250,507
Weighted-Average Exercise Price, Outstanding	$ 24.56	$ 21.66	$ 19.36
Weighted-Average Exercise Price, Granted	42.73	54.66	47.82
Weighted-Average Exercise Price, Exercised	5.54	12.50	13.69
Weighted-Average Exercise Price, Forfeited	53.50	56.97	55.07
Weighted-Average Exercise Price, Expired	54.35	36.31	14.19
Weighted-Average Exercise Price, Outstanding	28.31	24.56	21.66
Weighted-Average Exercise Price, Exercisable	24.93
Weighted-Average Grant-date Fair Value, Granted	$ 21.75	$ 28.28	$ 18.76
Total Intrinsic Value of options Exercised	$ 8,867	$ 7,446	$ 10,788
Weighted-Average Remaining Contractual Term, Outstanding		4 years 6 months 3 days
Weighted-Average Remaining Contractual Term, Exercisable		3 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding		$ 22,274
Aggregate Intrinsic Value, Exercisable		$ 22,273