Segment Reporting (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Oct. 31, 2017	Oct. 31, 2016		Oct. 31, 2017	Oct. 31, 2016
Segment Reporting Information [Line Items]
Net sales		$ 101,349	$ 72,522		$ 281,494	$ 208,480
Operating income		17,829	7,389		47,748	22,135
Administrative and general expenses	[1]	(5,990)	(4,764)		(17,247)	(13,986)
Applied Technology [Member]
Segment Reporting Information [Line Items]
Net sales		25,319	25,203		94,233	79,327
Operating income	[2]	5,357	6,415		25,447	20,280
Engineered Films [Member]
Segment Reporting Information [Line Items]
Net sales		65,108	38,551		157,691	104,307
Operating income	[2]	17,115	7,129		35,386	17,666
Aerostar [Member]
Segment Reporting Information [Line Items]
Inventory Write-down			2,278			2,278
Net sales		11,103	9,003		30,078	25,313
Operating income	[2]	1,359	(1,375)	[3]	4,165	(1,804)	[3]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	[4]	(181)	(235)		(508)	(467)
Operating income	[4]	(12)	(16)		(3)	(21)
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income		$ 23,819	$ 12,153		$ 64,995	$ 36,121

[1] (d) At the segment level, operating income (loss) does not include an allocation of general and administrative expenses and, as a result, "General and administrative expenses" are reported as a deduction from "Total reportable segment income" to reconcile to "Operating income" reported in the Consolidated Statements of Income and Comprehensive Income.

[2] (b) At the segment level, operating income (loss) does not include an allocation of general and administrative expenses.

[3] (c) The three- and nine-month periods ended October 31, 2016 include inventory write-downs of $2,278 as a result of a strategic decision to narrow certain radar product offerings.

[4]
^(a) Intersegment sales for both fiscal 2018 and 2017 were primarily sales from Engineered Films to Aerostar.