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Summary of Significant Accounting Policies - Summary of Fair Value Hierarchy for Financial Assets and Liabilities Measured Recurring and Nonrecurring Basis (Detail)
$ in Thousands
Apr. 30, 2020
USD ($)
compensation_plan
Apr. 30, 2019
USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets $ 2,572 $ 3,133
Financial Liabilities $ 2,899 3,520
Number of non-qualified compensation plans maintained | compensation_plan 2  
Trading Securities Held in Non-Qualified Compensation Plans    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets $ 2,485 3,057
Cash Surrender Value of Life Insurance Policies    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets 87 76
Non Qualified Compensation Plans    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Liabilities 2,899 3,519
Interest Rate Swap Derivatives    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Liabilities 0 1
Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets 2,485 3,057
Level 1 | Trading Securities Held in Non-Qualified Compensation Plans    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets 2,485 3,057
Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets 87 76
Financial Liabilities 2,899 3,520
Level 2 | Cash Surrender Value of Life Insurance Policies    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Assets 87 76
Level 2 | Non Qualified Compensation Plans    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Liabilities 2,899 3,519
Level 2 | Interest Rate Swap Derivatives    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Financial Liabilities $ 0 $ 1