Segment Information (Details) - USD ($)	3 Months Ended												12 Months Ended
	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	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, 2020	Jul. 31, 2019	Jul. 31, 2018
Segment Reporting Information, Profit (Loss)
Net sales	$ 149,673,000	$ 135,121,000	$ 161,654,000	$ 170,267,000	$ 176,372,000	$ 170,448,000	$ 164,133,000	$ 160,844,000	$ 167,435,000	$ 147,854,000	$ 133,731,000	$ 121,569,000	$ 616,715,000	$ 671,797,000	$ 570,589,000
Operating income (loss)													15,174,000	41,407,000	35,075,000
Net income (loss)	1,126,000	$ (3,989,000)	$ 3,495,000	$ 6,388,000	6,135,000	$ 7,612,000	$ 7,826,000	$ 3,468,000	7,458,000	$ 8,210,000	$ 15,761,000	$ (1,660,000)	7,020,000	25,041,000	29,769,000
Provision for (benefit from) income taxes													2,290,000	3,869,000	(5,143,000)
Interest (income) and other													(190,000)	35,000	254,000
Write-off of deferred financing costs													0	3,217,000	0
Interest expense													6,054,000	9,245,000	10,195,000
Amortization of stock-based compensation													9,275,000	11,427,000	8,569,000
Amortization of intangibles													21,595,000	18,320,000	21,075,000
Depreciation													10,561,000	11,927,000	13,655,000
Estimated contract settlement costs													444,000	6,351,000	0
Settlement of intellectual property litigation													0	(3,204,000)	0
Acquisition plan expenses													20,754,000	5,871,000	0
Facility exit costs														1,373,000
Adjusted EBITDA													77,803,000	93,472,000	78,374,000
Purchases of property, plant and equipment													7,225,000	8,785,000	8,642,000
Long-lived assets acquired in connection with acquisitions													38,451,000	60,693,000
Total assets	929,647,000				887,711,000				845,157,000				929,647,000	887,711,000	845,157,000
Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales													353,730,000	357,293,000
Government Solutions
Segment Reporting Information, Profit (Loss)
Net sales													262,985,000	314,504,000
Operating Segments | Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales													353,730,000	357,293,000	345,076,000
Operating income (loss)													34,820,000	36,053,000	40,837,000
Net income (loss)													34,414,000	35,888,000	40,297,000
Provision for (benefit from) income taxes													410,000	19,000	270,000
Interest (income) and other													(31,000)	75,000	151,000
Write-off of deferred financing costs														0
Interest expense													27,000	71,000	119,000
Amortization of stock-based compensation													0	0	0
Amortization of intangibles													17,325,000	14,944,000	17,699,000
Depreciation													8,347,000	9,265,000	9,479,000
Estimated contract settlement costs													444,000	6,351,000
Settlement of intellectual property litigation														0
Acquisition plan expenses													751,000	0
Facility exit costs														0
Adjusted EBITDA													61,687,000	66,613,000	68,015,000
Purchases of property, plant and equipment													5,281,000	6,293,000	7,151,000
Long-lived assets acquired in connection with acquisitions													6,060,000	60,693,000
Total assets	647,964,000				662,580,000				610,166,000				647,964,000	662,580,000	610,166,000
Operating Segments | Government Solutions
Segment Reporting Information, Profit (Loss)
Net sales													262,985,000	314,504,000	225,513,000
Operating income (loss)													19,988,000	28,997,000	10,950,000
Net income (loss)													20,232,000	29,029,000	10,835,000
Provision for (benefit from) income taxes													(100,000)	0	0
Interest (income) and other													(169,000)	(41,000)	112,000
Write-off of deferred financing costs														0
Interest expense													25,000	9,000	3,000
Amortization of stock-based compensation													0	0	0
Amortization of intangibles													4,270,000	3,376,000	3,376,000
Depreciation													1,446,000	1,891,000	3,088,000
Estimated contract settlement costs													0	0
Settlement of intellectual property litigation														0
Acquisition plan expenses													0	0
Facility exit costs														1,373,000
Adjusted EBITDA													25,704,000	35,637,000	17,414,000
Purchases of property, plant and equipment													1,617,000	1,902,000	901,000
Long-lived assets acquired in connection with acquisitions													32,391,000	0
Total assets	232,052,000				186,438,000				195,924,000				232,052,000	186,438,000	195,924,000
Unallocated
Segment Reporting Information, Profit (Loss)
Net sales													0	0	0
Operating income (loss)													(39,634,000)	(23,643,000)	(16,712,000)
Net income (loss)													(47,626,000)	(39,876,000)	(21,363,000)
Provision for (benefit from) income taxes													1,980,000	3,850,000	(5,413,000)
Interest (income) and other													10,000	1,000	(9,000)
Write-off of deferred financing costs														3,217,000
Interest expense													6,002,000	9,165,000	10,073,000
Amortization of stock-based compensation														11,427,000	8,569,000
Amortization of intangibles													0	0	0
Depreciation													768,000	771,000	1,088,000
Estimated contract settlement costs													0	0
Settlement of intellectual property litigation														(3,204,000)
Acquisition plan expenses													20,003,000	5,871,000
Facility exit costs														0
Adjusted EBITDA													(9,588,000)	(8,778,000)	(7,055,000)
Purchases of property, plant and equipment													327,000	590,000	590,000
Long-lived assets acquired in connection with acquisitions													0	0
Total assets	$ 49,631,000				$ 38,693,000				$ 39,067,000				49,631,000	38,693,000	39,067,000
Intersegment Eliminations | Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales													$ 9,837,000	$ 17,371,000	$ 9,630,000