Segment Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Jul. 31, 2017
Segment Reporting Information [Line Items]
Net sales	$ 133,731,000	$ 139,028,000	$ 255,300,000	$ 274,814,000
Operating income (loss)	4,883,000	12,849,000	5,105,000	12,121,000
Net income (loss)	15,761,000	6,585,000	14,101,000	4,096,000
Provision for (benefit from) income taxes	(13,349,000)	3,486,000	(14,094,000)	1,924,000
Interest (income) and other expense	(48,000)	(74,000)	(9,000)	(76,000)
Interest expense	2,519,000	2,852,000	5,107,000	6,177,000
Amortization of stock-based compensation	1,080,000	1,019,000	1,827,000	1,989,000
Amortization of intangibles	5,268,000	6,032,000	10,537,000	12,087,000
Depreciation	3,317,000	3,568,000	6,663,000	7,317,000
Settlement of intellectual property litigation	0	(9,979,000)	0	(9,979,000)
Adjusted EBITDA	14,548,000	13,489,000	24,132,000	23,535,000
Purchases of property, plant and equipment	1,728,000	2,072,000	2,836,000	4,147,000
Total assets	822,651,000	883,508,000	822,651,000	883,508,000	$ 832,063,000
Unallocated
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Operating income (loss)	(3,740,000)	4,647,000	(7,669,000)	(1,679,000)
Net income (loss)	7,116,000	(1,507,000)	1,396,000	(9,512,000)
Provision for (benefit from) income taxes	(13,342,000)	3,351,000	(14,093,000)	1,766,000
Interest (income) and other expense	(4,000)	9,000	(11,000)	12,000
Interest expense	2,490,000	2,794,000	5,039,000	6,055,000
Amortization of stock-based compensation	1,080,000	1,019,000	1,827,000	1,989,000
Amortization of intangibles	0	0	0	0
Depreciation	272,000	387,000	559,000	798,000
Settlement of intellectual property litigation		(9,979,000)		(9,979,000)
Adjusted EBITDA	(2,388,000)	(3,926,000)	(5,283,000)	(8,871,000)
Purchases of property, plant and equipment	121,000	7,000	177,000	77,000
Total assets	40,809,000	66,326,000	40,809,000	66,326,000
Interest expense related to Credit Facility	2,350,000	2,708,000	4,815,000	5,883,000
Commercial Solutions Segment | Operating Segments
Segment Reporting Information [Line Items]
Net sales	85,824,000	82,103,000	161,938,000	158,281,000
Operating income (loss)	8,922,000	5,864,000	13,714,000	8,962,000
Net income (loss)	8,958,000	5,730,000	13,660,000	8,743,000
Provision for (benefit from) income taxes	(7,000)	135,000	(1,000)	158,000
Interest (income) and other expense	(58,000)	(60,000)	(10,000)	(62,000)
Interest expense	29,000	59,000	65,000	123,000
Amortization of stock-based compensation	0	0	0	0
Amortization of intangibles	4,424,000	4,413,000	8,849,000	8,849,000
Depreciation	2,457,000	2,429,000	4,900,000	5,016,000
Settlement of intellectual property litigation		0		0
Adjusted EBITDA	15,803,000	12,706,000	27,463,000	22,827,000
Purchases of property, plant and equipment	1,418,000	1,652,000	2,377,000	3,647,000
Total assets	602,872,000	620,147,000	602,872,000	620,147,000
Commercial Solutions Segment | Intersegment Eliminations
Segment Reporting Information [Line Items]
Intersegment sales	2,328,000	3,059,000	4,949,000	6,485,000
Government Solutions Segment | Operating Segments
Segment Reporting Information [Line Items]
Net sales	47,907,000	56,925,000	93,362,000	116,533,000
Operating income (loss)	(299,000)	2,338,000	(940,000)	4,838,000
Net income (loss)	(313,000)	2,362,000	(955,000)	4,865,000
Provision for (benefit from) income taxes	0	0	0	0
Interest (income) and other expense	14,000	(23,000)	12,000	(26,000)
Interest expense	0	(1,000)	3,000	(1,000)
Amortization of stock-based compensation	0	0	0	0
Amortization of intangibles	844,000	1,619,000	1,688,000	3,238,000
Depreciation	588,000	752,000	1,204,000	1,503,000
Settlement of intellectual property litigation		0		0
Adjusted EBITDA	1,133,000	4,709,000	1,952,000	9,579,000
Purchases of property, plant and equipment	189,000	413,000	282,000	423,000
Total assets	$ 178,970,000	$ 197,035,000	$ 178,970,000	$ 197,035,000