Organization and Significant Accounting Policies - Long-Lived Assets (Details) - USD ($)	3 Months Ended	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Long-Lived Assets
Impairment loss			$ 4,398,000	$ 255,000
Machinery and equipment | Minimum
Long-Lived Assets
Estimated useful life		2 years
Machinery and equipment | Maximum
Long-Lived Assets
Estimated useful life		7 years
Computer equipment and software | Minimum
Long-Lived Assets
Estimated useful life		2 years
Computer equipment and software | Maximum
Long-Lived Assets
Estimated useful life		5 years
Furniture and fixtures | Minimum
Long-Lived Assets
Estimated useful life		3 years
Furniture and fixtures | Maximum
Long-Lived Assets
Estimated useful life		7 years
UAS Quantix Solution
Long-Lived Assets
Impairment loss	$ 4,398,000