Goodwill and Intangible Assets - Changes in Carrying Value of Goodwill By Reportable Segment (Detail) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 613,943	$ 578,298
Business acquisitions adjustment, increase in goodwill	2,643
Additions		38,926
Exchange rate fluctuations	10,083	(3,281)
Goodwill, Ending Balance	626,669	613,943
Operating Segments \| Consulting
Goodwill [Line Items]
Goodwill, Beginning Balance	173,014	173,147
Exchange rate fluctuations	396	(133)
Goodwill, Ending Balance	173,410	173,014
Operating Segments \| Executive Search \| North America
Goodwill [Line Items]
Goodwill, Beginning Balance	45,721	46,571
Exchange rate fluctuations	2,777	(850)
Goodwill, Ending Balance	48,498	45,721
Operating Segments \| Executive Search \| EMEA
Goodwill [Line Items]
Goodwill, Beginning Balance	44,494	45,480
Exchange rate fluctuations	2,955	(986)
Goodwill, Ending Balance	47,449	44,494
Operating Segments \| Executive Search \| Asia Pacific
Goodwill [Line Items]
Goodwill, Beginning Balance	972	972
Goodwill, Ending Balance	972	972
Operating Segments \| Digital
Goodwill [Line Items]
Goodwill, Beginning Balance	322,727	284,214
Business acquisitions adjustment, increase in goodwill	2,643
Additions		38,926
Exchange rate fluctuations	1,258	(413)
Goodwill, Ending Balance	326,628	322,727
Operating Segments \| RPO & Professional Search
Goodwill [Line Items]
Goodwill, Beginning Balance	27,015	27,914
Exchange rate fluctuations	2,697	(899)
Goodwill, Ending Balance	$ 29,712	$ 27,015

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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