Presentation and Summary of Significant Accounting Policies - Acquisition-Related Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of acquisition-related intangibles	$ 285	$ 388	$ 580
Finite-Lived Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of acquisition-related intangibles	1,600	2,400	1,800
Operating Expense
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of acquisition-related intangibles	300	400	600
Cost of License Fees
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of acquisition-related intangibles	1,300	2,000	$ 1,200
Acquired Finite Lived Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Acquisition-related intangible assets	8,140	8,140
Accumulated amortization	(7,008)	(5,408)
Total amortization expense	$ 1,132	2,732
Acquired Finite Lived Intangible Assets | Current Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization in Years	3 years
Acquisition-related intangible assets	$ 6,000	6,000
Acquired Finite Lived Intangible Assets | Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization in Years	8 years
Acquisition-related intangible assets	$ 1,700	1,700
Acquired Finite Lived Intangible Assets | Non-compete
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization in Years	3 years
Acquisition-related intangible assets	$ 100	100
Acquired Finite Lived Intangible Assets | Trademarks
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization in Years	3 years
Acquisition-related intangible assets	$ 340	$ 340