Business Segments and Major Customer Information - Sales to countries outside the United States (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Jan. 31, 2019	[1]	Oct. 31, 2018	[1],[2]	Jul. 31, 2018	[2]	Apr. 30, 2018	[2]	Jan. 31, 2018	[1]	Oct. 31, 2017	[1],[2]	Jul. 31, 2017	[2]	Apr. 30, 2017	[2]	Jan. 31, 2019		Jan. 31, 2018		Jan. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 88,022		$ 104,833		$ 102,684		$ 111,129		$ 95,823		$ 101,349		$ 86,610		$ 93,535		$ 406,668	[3],[4]	$ 377,317	[3],[4]	$ 277,395	[4]
All foreign [Member]
Segment Reporting Information [Line Items]
Net sales																	48,329		41,556		35,528
Canada
Segment Reporting Information [Line Items]
Net sales																	12,492		12,940		13,969
Europe
Segment Reporting Information [Line Items]
Net sales																	15,786		13,864		13,924
Latin America
Segment Reporting Information [Line Items]
Net sales																	5,950		4,439		3,402
Asia
Segment Reporting Information [Line Items]
Net sales																	7,240		4,074		1,535
Other foreign sales
Segment Reporting Information [Line Items]
Net sales																	6,861		6,239		2,698
United States
Segment Reporting Information [Line Items]
Net sales																	$ 358,339		$ 335,761		$ 241,867

[1] In the third and fourth quarter of fiscal year 2018 hurricane recovery film net sales were $8,424 and $15,801, respectively. Sales of hurricane recovery film in fiscal year 2019 were $8,919, $1,510 and $4,065 for the first, third, and fourth quarters, respectively.

[2] In September of fiscal year 2018, the Company acquired CLI. For the first seven months of fiscal 2019 CLI contributed a total of $21,568 in sales and for the first seven months of fiscal 2018 the division generated $4,109 in sales to CLI as a customer.

[3] In September of fiscal year 2018, the Company acquired CLI. For the first seven months of fiscal 2019 CLI contributed a total of $21,568 in sales and for the first seven months of fiscal 2018 the division generated $4,109 in sales to CLI as a customer. Additionally, sales of hurricane recovery film in fiscal years 2019 and 2018 were $14,494 and $24,225, respectively

[4] Aerostar divested its client private business in the first quarter of fiscal 2019. Net sales from the client private business were $283, $5,592, and $5,886 in fiscal years 2019, 2018 and 2017, respectively. Operating profits for the client private business were not material for these periods.