Revenue (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net sales	$ 127,149	$ 99,265
Gross profit	67,524	49,137
Net income / (loss)	8,115	$ (4,159)
ASU 2014-09 | Amounts Without Adoption
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net sales	124,974
Gross profit	66,525
Net income / (loss)	7,597
ASU 2014-09 | Impact of Adoption
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Net sales	2,175
Gross profit	999
Net income / (loss)	$ 518