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Gross Unrealized Losses and Fair Value of Marketable Securities (Detail) - USD ($)
$ in Thousands
Jan. 31, 2022
Jan. 31, 2021
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value $ 407,237 $ 192,533
Less Than 12 Months, Unrealized Losses (4,518) (330)
12 Months or Greater, Fair Value 21,228  
12 Months or Greater, Unrealized Losses (40)  
Total, Fair Value 428,465 192,533
Total, Unrealized Losses (4,558) (330)
Municipal And Pre-Refunded Municipal Bonds    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value 162,081 90,308
Less Than 12 Months, Unrealized Losses (1,162) (99)
12 Months or Greater, Fair Value 7,118  
12 Months or Greater, Unrealized Losses (23)  
Total, Fair Value 169,199 90,308
Total, Unrealized Losses (1,185) (99)
Corporate Bonds    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value 212,861 91,432
Less Than 12 Months, Unrealized Losses (2,661) (177)
12 Months or Greater, Fair Value 14,110  
12 Months or Greater, Unrealized Losses (17)  
Total, Fair Value 226,971 91,432
Total, Unrealized Losses (2,678) (177)
US Treasury Securities    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value 20,137  
Less Than 12 Months, Unrealized Losses (84)  
Total, Fair Value 20,137  
Total, Unrealized Losses (84)  
Mutual Funds, Held in Rabbi Trust    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value 11,813 10,793
Less Than 12 Months, Unrealized Losses (606) (54)
Total, Fair Value 11,813 10,793
Total, Unrealized Losses (606) $ (54)
Federal Government Agencies    
Schedule of Available-for-sale Securities [Line Items]    
Less Than 12 Months, Fair Value 345  
Less Than 12 Months, Unrealized Losses (5)  
Total, Fair Value 345  
Total, Unrealized Losses $ (5)