Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
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	$ 9,547	$ 6,737
Pharmacology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	9,413	6,530
Personalized oncology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	113	180
Other
Disaggregation of Revenue [Line Items]
Oncology services revenue	$ 21	$ 27