Stock-based Compensation - Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Oct. 31, 2017 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding | shares	1,703,524
Shares, Granted | shares	91,300
Shares, Exercised | shares	(135,180)
Shares, Forfeited | shares	(21,057)
Shares, Expired | shares	(18,045)
Shares, Outstanding | shares	1,620,542
Shares, Exercisable | shares	1,351,300
Weighted-Average Exercise Price, Outstanding	$ 21.66
Weighted-Average Exercise Price, Granted	52.57
Weighted-Average Exercise Price, Exercised	12.34
Weighted-Average Exercise Price, Forfeited	56.87
Weighted-Average Exercise Price, Expired	30.88
Weighted-Average Exercise Price, Outstanding	23.62
Weighted-Average Exercise Price, Exercisable	17.95
Weighted-Average Grant-date Fair Value, Granted	$ 27.20
Total Intrinsic Value Of Options Exercised | $	$ 5,569
Weighted-Average Remaining Contractual Term, Outstanding	4 years 8 months 27 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 22 days
Aggregate Intrinsic Value, Outstanding | $	$ 55,763
Aggregate Intrinsic Value, Exercisable | $	$ 53,559