Business Segments and Major Customer Information - Sales to countries outside the United States (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 377,317	$ 277,395	$ 258,229
All foreign [Member]
Segment Reporting Information [Line Items]
Net sales	41,556	35,528	27,849
Canada
Segment Reporting Information [Line Items]
Net sales	12,940	13,969	11,789
Europe
Segment Reporting Information [Line Items]
Net sales	13,864	13,924	10,526
Latin America
Segment Reporting Information [Line Items]
Net sales	4,439	3,402	2,676
Asia
Segment Reporting Information [Line Items]
Net sales	4,074	1,535	482
Other foreign sales
Segment Reporting Information [Line Items]
Net sales	6,239	2,698	2,376
United States
Segment Reporting Information [Line Items]
Net sales	$ 335,761	$ 241,867	$ 230,380