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Fair Value - Narrative (Detail) - USD ($)
9 Months Ended
Jan. 31, 2021
May 03, 2020
Feb. 02, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Short-term investments - available for sale $ 5,500,000 $ 923,000 $ 7,600,000
Amortized cost of held-to-maturity investments 10,300,000 6,300,000 5,400,000
Fair value of held-to-maturity investments 10,300,000 6,400,000 5,400,000
Long-term investments (Rabbi Trust) $ 8,232,000 7,834,000 [1] 7,804,000
Minimum [Member] | Investments (Held-To-Maturity) [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Investment maturity period 2 years    
Maximum [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Investment remaining maturity period 2 years    
Maximum [Member] | Investments (Held-To-Maturity) [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Investment maturity period 10 years    
Short-term Investments [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Accumulated unrealized gain (loss) on investments $ 30,000 9,000 48,000
Current Expected Credit Loses [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Accumulated unrealized gain (loss) on investments 30,000    
Long-term Investments (Rabbi Trust) [Member]      
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]      
Accumulated unrealized gain (loss) on investments $ 87,000 $ (19,000) $ 56,000
[1] Derived from audited financial statements.