Goodwill and Intangible Assets - Intangible Assets (Detail) - USD ($) $ in Thousands	Apr. 30, 2021	Apr. 30, 2020
Intangible Assets [Line Items]
Amortized intangible assets, Gross	$ 212,751	$ 212,751
Amortized intangible assets, Accumulated Amortization	(119,892)	(100,658)
Amortized intangible assets, Net	92,859	112,093
Exchange rate fluctuations	90	(167)
Total Intangible assets	92,949	111,926
Customer Lists
Intangible Assets [Line Items]
Amortized intangible assets, Gross	131,299	131,299
Amortized intangible assets, Accumulated Amortization	(76,489)	(64,762)
Amortized intangible assets, Net	54,810	66,537
Intellectual Property
Intangible Assets [Line Items]
Amortized intangible assets, Gross	69,100	69,100
Amortized intangible assets, Accumulated Amortization	(33,623)	(26,548)
Amortized intangible assets, Net	35,477	42,552
Database Rights
Intangible Assets [Line Items]
Amortized intangible assets, Gross	4,256	4,256
Amortized intangible assets, Accumulated Amortization	(4,234)	(4,202)
Amortized intangible assets, Net	22	54
Non-compete Agreements
Intangible Assets [Line Items]
Amortized intangible assets, Gross	910	910
Amortized intangible assets, Accumulated Amortization	(910)	(910)
Trademarks
Intangible Assets [Line Items]
Amortized intangible assets, Gross	7,186	7,186
Amortized intangible assets, Accumulated Amortization	(4,636)	(4,236)
Amortized intangible assets, Net	$ 2,550	$ 2,950