Share Based Compensation - Outstanding stock options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2019 USD ($) $ / shares shares
Number of options
Outstanding, beginning of period (in shares) | shares	702,950
Granted (in shares) | shares	55,810
Exercised (in shares) | shares	(390,630)
Outstanding, end of period (in shares) | shares	368,130
Weighted average exercise price
Outstanding, beginning of period (in usd per share) | $ / shares	$ 22.34
Granted (in usd per share) | $ / shares	35.05
Exercised (in usd per share) | $ / shares	23.48
Outstanding, end of period (in usd per share) | $ / shares	$ 23.06
Aggregate intrinsic value, Outstanding, end of period | $	$ 5,130
Weighted average remaining contractual term (years), Outstanding, end of period	2 years 4 months 28 days
Number of options, outstanding exercisable, end of period | shares	70,545
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, number | shares	368,130
Weighted average exercise price, Outstanding exercisable, end of period | $ / shares	$ 23.08
Share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding, weighted average exercise price | $ / shares	$ 23.06
Aggregate intrinsic value, Outstanding exercisable, end of period | $	$ 981
Weighted average remaining contractual term (years), Outstanding exercisable, end of period	1 year 8 months 15 days
Share-based compensation arrangement by share-based payment award, options, vested and expected to Vest, outstanding, weighted average remaining contractual term	2 years 4 months 28 days