Revenue - Disaggregation of Revenues (Details) - USD ($)	3 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 170,267,000	$ 160,844,000
Point in time
Disaggregation of Revenue [Line Items]
Revenues	75,509,000	90,568,000
Over time
Disaggregation of Revenue [Line Items]
Revenues	94,758,000	70,276,000
Firm fixed price
Disaggregation of Revenue [Line Items]
Revenues	143,272,000	139,901,000
Cost reimbursable
Disaggregation of Revenue [Line Items]
Revenues	26,995,000	20,943,000
U.S. government
Disaggregation of Revenue [Line Items]
Revenues	69,521,000	71,044,000
Domestic
Disaggregation of Revenue [Line Items]
Revenues	61,395,000	50,511,000
Total United States
Disaggregation of Revenue [Line Items]
Revenues	130,916,000	121,555,000
International
Disaggregation of Revenue [Line Items]
Revenues	39,351,000	39,289,000
Commercial Solutions
Disaggregation of Revenue [Line Items]
Revenues	94,314,000	77,973,000
Commercial Solutions | Point in time
Disaggregation of Revenue [Line Items]
Revenues	37,723,000	37,945,000
Commercial Solutions | Over time
Disaggregation of Revenue [Line Items]
Revenues	56,591,000	40,028,000
Commercial Solutions | Firm fixed price
Disaggregation of Revenue [Line Items]
Revenues	92,548,000	76,290,000
Commercial Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Revenues	1,766,000	1,683,000
Commercial Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Revenues	16,748,000	14,220,000
Commercial Solutions | Domestic
Disaggregation of Revenue [Line Items]
Revenues	53,354,000	42,237,000
Commercial Solutions | Total United States
Disaggregation of Revenue [Line Items]
Revenues	70,102,000	56,457,000
Commercial Solutions | International
Disaggregation of Revenue [Line Items]
Revenues	24,212,000	21,516,000
Government Solutions
Disaggregation of Revenue [Line Items]
Revenues	75,953,000	82,871,000
Government Solutions | Point in time
Disaggregation of Revenue [Line Items]
Revenues	37,786,000	52,623,000
Government Solutions | Over time
Disaggregation of Revenue [Line Items]
Revenues	38,167,000	30,248,000
Government Solutions | Firm fixed price
Disaggregation of Revenue [Line Items]
Revenues	50,724,000	63,611,000
Government Solutions | Cost reimbursable
Disaggregation of Revenue [Line Items]
Revenues	25,229,000	19,260,000
Government Solutions | U.S. government
Disaggregation of Revenue [Line Items]
Revenues	52,773,000	56,824,000
Government Solutions | Domestic
Disaggregation of Revenue [Line Items]
Revenues	8,041,000	8,274,000
Government Solutions | Total United States
Disaggregation of Revenue [Line Items]
Revenues	60,814,000	65,098,000
Government Solutions | International
Disaggregation of Revenue [Line Items]
Revenues	$ 15,139,000	$ 17,773,000