Organization and Significant Accounting Policies Long-Lived Assets (Details)	12 Months Ended
	Apr. 30, 2017
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