Stock-based Compensation - Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jul. 31, 2017 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding | shares	1,703,524
Shares, Granted | shares	72,400
Shares, Exercised | shares	(89,829)
Shares, Forfeited | shares	(13,818)
Shares, Expired | shares	(5,495)
Shares, Outstanding | shares	1,666,782
Shares, Exercisable | shares	1,366,052
Weighted-Average Exercise Price, Outstanding	$ 21.66
Weighted-Average Exercise Price, Granted	55.69
Weighted-Average Exercise Price, Exercised	13.13
Weighted-Average Exercise Price, Forfeited	56.69
Weighted-Average Exercise Price, Expired	68.57
Weighted-Average Exercise Price, Outstanding	23.15
Weighted-Average Exercise Price, Exercisable	16.81
Weighted-Average Grant-date Fair Value, Granted	$ 28.84
Total Intrinsic Value Of Options Exercised | $	$ 3,783
Weighted-Average Remaining Contractual Term, Outstanding	4 years 10 months 6 days
Weighted-Average Remaining Contractual Term, Exercisable	4 years 1 month 10 days
Aggregate Intrinsic Value, Outstanding | $	$ 48,972
Aggregate Intrinsic Value, Exercisable | $	$ 47,343