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Defined Benefit Pension Plans - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Oct. 31, 2020
Oct. 31, 2020
Oct. 31, 2019
Retirement Benefits [Abstract]      
Employer contributions $ 0 $ 0  
Employer contributions paid during the remainder of fiscal year $ 30,000 $ 30,000  
Assumed as expected long-term rate of return   7.75% 7.75%