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Fair Value of Financial Instruments - Narrative (Detail) - USD ($)
9 Months Ended
Feb. 02, 2020
Apr. 28, 2019
Jan. 27, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Held to maturity investments $ 5,400,000 $ 5,000,000 $ 13,500,000
Held to maturity investments, fair value 5,400,000 5,000,000 13,500,000
Short-term investments - Available for Sale 7,580,000 0 0
Long-term investments (Rabbi Trust) 7,804,000 7,081,000 [1] 6,834,000
Short-term Investments [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Accumulated unrealized gain (loss) on investments 48,000    
Long-term investments (Rabbi Trust) [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Accumulated unrealized gain (loss) on investments $ 56,000 $ 40,000 $ 9,000
Minimum [Member] | Held-To-Maturity Investments [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term investments, maturity period 1 year    
Maximum [Member] | Held-To-Maturity Investments [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Long-term investments, maturity period 3 years    
[1] Derived from audited financial statements.