Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2022	Jan. 31, 2021
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	$ 13,193	$ 10,812	$ 36,232	$ 30,476
Revenue Benchmark \| Customer Concentration Risk \| Pharmaceutical Services And Other TOS Customer
Disaggregation of Revenue [Line Items]
Customer revenue (in Percent)	11.00%	10.00%	14.00%	10.00%
Pharmacology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	$ 12,622	$ 10,745	$ 34,468	$ 30,199
Other TOS revenue
Disaggregation of Revenue [Line Items]
Oncology services revenue	546	62	1,715	122
Personalized oncology services
Disaggregation of Revenue [Line Items]
Oncology services revenue	$ 25	$ 5	$ 49	$ 155

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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