Accrued Expenses and Other Current Liabilities - Narrative (Details)	9 Months Ended	12 Months Ended
	Apr. 30, 2020 USD ($)	Jul. 31, 2018 USD ($) credit	Aug. 01, 2019 USD ($)	Jul. 31, 2019 USD ($)	Apr. 30, 2019 USD ($)	Aug. 01, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets, net	$ 31,942,000			$ 0
Operating lease liabilities, current	$ 8,480,000			0
Minimum coverage period of product warranty from the date of shipment	1 year
Accrued warranty obligations	$ 15,504,000	$ 11,738,000		15,968,000	$ 14,263,000
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued expenses and other current liabilities			$ 2,934,000
Operating lease right-of-use assets, net			35,825,000
Estimated facility exit costs			568,000
Operating lease liabilities, current			568,000
ASU 2016-02, Accrued expenses and other current liabilities adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Short-term deferred rent liabilities			2,366,000
Operating lease right-of-use assets, net			2,366,000
Estimated facility exit costs			568,000
Operating lease liabilities, current			$ 568,000
Difference between Revenue Guidance in Effect before and after Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued warranty obligations						$ (1,679,000)
TeleCommunication Systems Inc. | TCS 911 call handling software solution
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued warranty obligations	2,604,000			$ 3,999,000
Full and final warranty settlement with AT&T | TeleCommunication Systems Inc. | TCS 911 call handling software solution
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of monthly credits issued | credit		36
Amount of monthly credit		$ 153,000
Present value of monthly credits	$ 748,000