Segment Information (Details)	3 Months Ended		6 Months Ended
	Jan. 31, 2021 USD ($) ft²	Jan. 31, 2020 USD ($)	Jan. 31, 2021 USD ($) ft²	Jan. 31, 2020 USD ($)	Jul. 31, 2020 USD ($)
Segment Reporting Information, Profit (Loss)
Net sales	$ 161,292,000	$ 161,654,000	$ 296,510,000	$ 331,921,000
Operating income (loss)	5,402,000	6,234,000	(80,314,000)	15,494,000
Net income (loss)	4,205,000	3,495,000	(81,635,000)	9,883,000
(Benefit from) provision for income taxes	(155,000)	1,117,000	(2,394,000)	2,262,000
Interest (income) and other	(66,000)	6,000	0	(71,000)
Interest expense	1,418,000	1,616,000	3,715,000	3,420,000
Amortization of stock-based compensation	1,287,000	1,238,000	1,986,000	2,117,000
Amortization of intangibles	4,795,000	5,229,000	10,361,000	10,435,000
Depreciation	2,457,000	2,721,000	5,009,000	5,372,000
Estimated contract settlement costs		(262,000)		(32,000)
Acquisition plan expenses	3,357,000	6,025,000	94,540,000	8,414,000
Restructuring costs	601,000	6,025,000	601,000
COVID-19 related costs	160,000		160,000
Adjusted EBITDA	18,059,000	21,185,000	32,343,000	41,800,000
Purchases of property, plant and equipment	2,796,000	1,258,000	3,686,000	2,508,000
Long-lived assets acquired in connection with acquisitions		31,131,000		31,131,000
Total assets	$ 946,595,000	949,942,000	946,595,000	949,942,000	$ 929,647,000
Incremental interest expense on financing commitment letter			$ 1,178,000
Chandler, Arizona
Segment Reporting Information, Profit (Loss)
Area of property (in sq ft) | ft²	146,000		146,000
Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales	$ 87,825,000	96,122,000	$ 169,627,000	190,436,000
Government Solutions
Segment Reporting Information, Profit (Loss)
Net sales	73,467,000	65,532,000	126,883,000	141,485,000
Operating Segments | Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales	87,825,000	96,122,000	169,627,000	190,436,000
Operating income (loss)	9,371,000	12,619,000	18,121,000	22,460,000
Net income (loss)	9,283,000	12,702,000	17,598,000	22,569,000
(Benefit from) provision for income taxes	217,000	(112,000)	556,000	(99,000)
Interest (income) and other	(129,000)	20,000	(33,000)	(27,000)
Interest expense	0	9,000	0	17,000
Amortization of stock-based compensation	0	0	0	0
Amortization of intangibles	4,286,000	4,362,000	8,573,000	8,724,000
Depreciation	1,934,000	2,183,000	3,930,000	4,379,000
Estimated contract settlement costs		(262,000)		(32,000)
Acquisition plan expenses	0		(1,052,000)	0
Restructuring costs	601,000	0	601,000
COVID-19 related costs	0		0
Adjusted EBITDA	16,192,000	18,902,000	30,173,000	35,531,000
Purchases of property, plant and equipment	1,575,000	915,000	1,964,000	1,915,000
Long-lived assets acquired in connection with acquisitions		0		0
Total assets	672,209,000	672,336,000	672,209,000	672,336,000
Operating Segments | Government Solutions
Segment Reporting Information, Profit (Loss)
Net sales	73,467,000	65,532,000	126,883,000	141,485,000
Operating income (loss)	5,460,000	5,003,000	8,045,000	12,086,000
Net income (loss)	5,695,000	5,016,000	8,386,000	12,111,000
(Benefit from) provision for income taxes	(286,000)	0	(412,000)	0
Interest (income) and other	47,000	(13,000)	7,000	(26,000)
Interest expense	4,000	0	64,000	1,000
Amortization of stock-based compensation	0	0	0	0
Amortization of intangibles	509,000	867,000	1,788,000	1,711,000
Depreciation	443,000	312,000	846,000	625,000
Estimated contract settlement costs		0		0
Acquisition plan expenses	0		0	0
Restructuring costs	0	0	0
COVID-19 related costs	160,000		160,000
Adjusted EBITDA	6,572,000	6,182,000	10,839,000	14,422,000
Purchases of property, plant and equipment	1,221,000	201,000	1,642,000	425,000
Long-lived assets acquired in connection with acquisitions		31,131,000		31,131,000
Total assets	240,618,000	233,221,000	240,618,000	233,221,000
Unallocated
Segment Reporting Information, Profit (Loss)
Net sales	0	0	0	0
Operating income (loss)	(9,429,000)	(11,388,000)	(106,480,000)	(19,052,000)
Net income (loss)	(10,773,000)	(14,223,000)	(107,619,000)	(24,797,000)
(Benefit from) provision for income taxes	(86,000)	1,229,000	(2,538,000)	2,361,000
Interest (income) and other	16,000	(1,000)	26,000	(18,000)
Interest expense	1,414,000	1,607,000	3,651,000	3,402,000
Amortization of stock-based compensation	1,287,000	1,238,000		2,117,000
Amortization of intangibles	0	0	0	0
Depreciation	80,000	226,000	233,000	368,000
Estimated contract settlement costs		0		0
Acquisition plan expenses	3,357,000		95,592,000	8,414,000
Restructuring costs	0	6,025,000
COVID-19 related costs	0		0
Adjusted EBITDA	(4,705,000)	(3,899,000)	(8,669,000)	(8,153,000)
Purchases of property, plant and equipment	0	142,000	80,000	168,000
Long-lived assets acquired in connection with acquisitions		0		0
Total assets	33,768,000	44,385,000	33,768,000	44,385,000
Intersegment Eliminations | Commercial Solutions
Segment Reporting Information, Profit (Loss)
Net sales	$ 944,000	$ 1,862,000	$ 1,795,000	$ 3,761,000