Revenue (Details) - USD ($)	3 Months Ended		9 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019	Jul. 31, 2019
Revenue from Contract with Customer [Abstract]
Allowance for doubtful accounts	$ 0		$ 0		$ 0
Contract costs, current	8,232,000		8,232,000		7,015,000
Contract costs, noncurrent	22,389,000		22,389,000		$ 23,375,000
Amortization of capitalized contract cost	2,200,000	$ 1,200,000	5,600,000	$ 3,600,000
Contract with customer, liability, revenue recognized	17,200,000		94,100,000
Remaining performance obligation, amount	$ 397,900,000		$ 397,900,000