Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2021	Jul. 31, 2020
Disaggregation of Revenue [Line Items]
Description of timing	The majority of the Company's revenue arrangements are service contracts that are complete within a year or less. There are a few contracts that range in duration between 1 and 3 years.
Oncology services revenue	$ 11,253	$ 9,547
Pharmacology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	10,703	9,412
Other TOS revenue
Disaggregation of Revenue [Line Items]
Oncology services revenue	526	21
Personalized oncology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	$ 24	$ 113