Interest expense, net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Interest Income (Expense), Net [Abstract]
Interest expense	$ 193	$ 139	$ 358	$ 392
Interest income	(36)	(42)	(44)	(69)
Interest expense, net	$ 157	$ 97	$ 314	$ 323