Revenue Revenue - Sale Information, Percent (Details)	3 Months Ended		9 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019
Concentration Risk [Line Items]
Entity wide revenue percentage by major customer type	100.00%	100.00%	100.00%	100.00%
U.S. government
Concentration Risk [Line Items]
Entity wide revenue percentage by major customer type	30.70%	38.90%	38.10%	42.70%
Domestic
Concentration Risk [Line Items]
Entity wide revenue percentage by major customer type	45.00%	34.70%	38.80%	32.70%
Total United States
Concentration Risk [Line Items]
Entity wide revenue percentage by major customer type	75.70%	73.60%	76.90%	75.40%
International
Concentration Risk [Line Items]
Entity wide revenue percentage by major customer type	24.30%	26.40%	23.10%	24.60%