Revenue (Details) - USD ($)	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Jul. 31, 2020
Revenue from Contract with Customer [Abstract]
Allowance for doubtful accounts	$ 0		$ 0
Contract costs, current	10,011,000		9,588,000
Contract costs, noncurrent	23,838,000		$ 25,221,000
Amortization of capitalized contract cost	2,200,000	$ 1,400,000
Contract with customer, liability, revenue recognized	47,000,000
Remaining performance obligation, amount	$ 539,000,000