Financial Instruments - Financial Instruments and Balance Sheet Classifications (Parenthetical) (Detail) - USD ($) $ in Millions |
3 Months Ended | ||
|---|---|---|---|
Jul. 31, 2021 |
Jul. 31, 2020 |
Apr. 30, 2021 |
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| Investments Debt And Equity Securities [Abstract] | |||
| Obligations for which assets are held in trust | $ 171.2 | $ 157.3 | |
| Gain on marketable securities | 5.2 | $ 11.5 | |
| Unvested obligations under deferred compensation plans | $ 24.7 | $ 26.5 | |
| X | ||||||||||
- Definition The amount of the liability included in the deferred compensation plans that is unvested and therefore the participants have not earned the right to. No definition available.
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| X | ||||||||||
- Definition Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of the liabilities for deferred compensation arrangements classified as other. No definition available.
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