11. Sale of Research and Development Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Income (loss) from discontinued operations, net of tax	$ 0	$ 0	$ 841
Discontinued Operations [Member] [Default Label]
Other income			125
Gain on sale of research and development assets before income taxes			1,000
Income tax expense			284
Income (loss) from discontinued operations, net of tax			$ 841

Amount after tax of income (loss) from a discontinued operation including the portion attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

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+ Details