Revenue - Narrative (Details) - USD ($)	3 Months Ended
	Oct. 31, 2019	Oct. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognized	$ 18,609,000	$ 23,127,000
Remaining performance obligation, amount	$ 648,343,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Estimated period to satisfy a substantial portion of remaining performance obligations	24 months