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Defined Benefit Pension Plans - Additional Information (Detail) - USD ($) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jan. 31, 2021 | Jan. 31, 2020 | Jan. 31, 2021 | Jan. 31, 2020
Retirement Benefits [Abstract] |  |  |  |
Employer contributions | $ 30,000 | $ 0 | $ 30,000 | $ 0
Assumed as expected long-term rate of return (as a percent) |  |  | 7.75% | 7.75%

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