Fee Revenue - Additional Information (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Apr. 30, 2020 |
Apr. 30, 2019 |
|
| Revenue From Contract With Customer [Abstract] | ||
| Contract liabilities, revenue recognized | $ 94.1 | $ 97.0 |
| Revenue recognized, remaining performance obligation | $ 608.5 | |
| Revenue, practical expedient, initial application and transition, completed contract, same reporting period | true | |
| Revenue, remaining performance obligation, optional exemption, performance obligation | true | |
| X | ||||||||||
- Definition Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Indicates (true false) whether practical expedient was elected under initial application of retrospective method not to restate completed contract beginning and ending in same annual reporting period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Indicates (true false) whether optional exemption was applied not to disclose amount of transaction price allocated to and explanation of expected timing of revenue recognition for remaining performance obligation, when contract has expected duration of one year or less or right to consideration corresponds directly to performance completed. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of transaction price allocated to performance obligation that has not been recognized as revenue. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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