Revenue (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020	Jul. 31, 2020
Revenue from Contract with Customer [Abstract]
Allowance for doubtful accounts	$ 0		$ 0		$ 0
Contract costs, current	10,768,000		10,768,000		9,588,000
Contract costs, noncurrent	24,623,000		24,623,000		$ 25,221,000
Amortization of capitalized contract cost	3,200,000	$ 2,000,000.0	5,400,000	$ 3,400,000
Contract with customer, liability, revenue recognized	35,000,000		83,000,000
Remaining performance obligation, amount	$ 588,000,000		$ 588,000,000