Segment Information (Details) - USD ($)	3 Months Ended												12 Months Ended
	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Segment Reporting Information, Profit (Loss)
Net sales	$ 176,372,000	$ 170,448,000	$ 164,133,000	$ 160,844,000	$ 167,435,000	$ 147,854,000	$ 133,731,000	$ 121,569,000	$ 147,762,000	$ 127,792,000	$ 139,028,000	$ 135,786,000	$ 671,797,000	$ 570,589,000	$ 550,368,000
Operating income (loss)													41,407,000	35,075,000	37,042,000
Net income (loss)	6,135,000	$ 7,612,000	$ 7,826,000	3,468,000	7,458,000	$ 8,210,000	$ 15,761,000	$ (1,660,000)	7,314,000	$ 4,417,000	$ 6,585,000	$ (2,489,000)	25,041,000	29,769,000	15,827,000
Provision for income taxes													3,869,000	(5,143,000)	9,654,000
Interest (income) and other													35,000	254,000	(68,000)
Write-off of deferred financing costs													3,217,000	0	0
Interest expense													9,245,000	10,195,000	11,629,000
Amortization of stock-based compensation													11,427,000	8,569,000	8,506,000
Amortization of intangibles													18,320,000	21,075,000	22,823,000
Depreciation and amortization of property, plant and equipment													11,927,000	13,655,000	14,354,000
Estimated contract settlement costs													6,351,000	0	0
Settlement of intellectual property litigation													(3,204,000)	0	(12,020,000)
Facility exit costs													1,373,000
Adjusted EBITDA													93,472,000	78,374,000	70,705,000
Purchases of property, plant and equipment													8,785,000	8,642,000	8,150,000
Long-lived assets acquired in connection with acquisitions													60,693,000
Total assets	887,711,000				845,157,000				832,063,000				887,711,000	845,157,000	832,063,000
Acquisition plan expenses													5,871,000	0	0
Prior Credit Facility
Segment Reporting Information, Profit (Loss)
Write-off of deferred financing costs				$ 3,217,000									3,217,000
Unallocated
Segment Reporting Information, Profit (Loss)
Net sales													0	0	0
Operating income (loss)													(23,643,000)	(16,712,000)	(5,585,000)
Net income (loss)													(39,876,000)	(21,363,000)	(26,465,000)
Provision for income taxes													3,850,000	(5,413,000)	9,396,000
Interest (income) and other													1,000	(9,000)	74,000
Write-off of deferred financing costs													3,217,000
Interest expense													9,165,000	10,073,000	11,410,000
Amortization of stock-based compensation													11,427,000	8,569,000	8,506,000
Amortization of intangibles													0	0	0
Depreciation and amortization of property, plant and equipment													771,000	1,088,000	1,478,000
Estimated contract settlement costs													0
Settlement of intellectual property litigation													(3,204,000)		(12,020,000)
Facility exit costs													0
Adjusted EBITDA													(8,778,000)	(7,055,000)	(7,621,000)
Purchases of property, plant and equipment													590,000	590,000	97,000
Long-lived assets acquired in connection with acquisitions													0
Total assets	38,693,000				39,067,000				40,393,000				38,693,000	39,067,000	40,393,000
Acquisition plan expenses													5,871,000
Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales													357,293,000
Commercial Solutions | Operating Segments
Segment Reporting Information, Profit (Loss)
Net sales													357,293,000	345,076,000	330,867,000
Operating income (loss)													36,053,000	40,837,000	33,234,000
Net income (loss)													35,888,000	40,297,000	32,871,000
Provision for income taxes													19,000	270,000	258,000
Interest (income) and other													75,000	151,000	(108,000)
Write-off of deferred financing costs													0
Interest expense													71,000	119,000	213,000
Amortization of stock-based compensation													0	0	0
Amortization of intangibles													14,944,000	17,699,000	17,698,000
Depreciation and amortization of property, plant and equipment													9,265,000	9,479,000	9,938,000
Estimated contract settlement costs													6,351,000
Settlement of intellectual property litigation													0		0
Facility exit costs													0
Adjusted EBITDA													66,613,000	68,015,000	60,870,000
Purchases of property, plant and equipment													6,293,000	7,151,000	7,007,000
Long-lived assets acquired in connection with acquisitions													60,693,000
Total assets	662,580,000				610,166,000				606,436,000				662,580,000	610,166,000	606,436,000
Acquisition plan expenses													0
Commercial Solutions | Intersegment Eliminations
Segment Reporting Information, Profit (Loss)
Net sales													17,371,000	9,630,000	12,492,000
Government Solutions
Segment Reporting Information, Profit (Loss)
Net sales													314,504,000
Government Solutions | Operating Segments
Segment Reporting Information, Profit (Loss)
Net sales													314,504,000	225,513,000	219,501,000
Operating income (loss)													28,997,000	10,950,000	9,393,000
Net income (loss)													29,029,000	10,835,000	9,421,000
Provision for income taxes													0	0	0
Interest (income) and other													(41,000)	112,000	(34,000)
Write-off of deferred financing costs													0
Interest expense													9,000	3,000	6,000
Amortization of stock-based compensation													0	0	0
Amortization of intangibles													3,376,000	3,376,000	5,125,000
Depreciation and amortization of property, plant and equipment													1,891,000	3,088,000	2,938,000
Estimated contract settlement costs													0
Settlement of intellectual property litigation													0		0
Facility exit costs													1,373,000
Adjusted EBITDA													35,637,000	17,414,000	17,456,000
Purchases of property, plant and equipment													1,902,000	901,000	1,046,000
Long-lived assets acquired in connection with acquisitions													0
Total assets	$ 186,438,000				$ 195,924,000				$ 185,234,000				186,438,000	$ 195,924,000	$ 185,234,000
Acquisition plan expenses													$ 0