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Marketable Securities - Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Oct. 31, 2023
Jan. 31, 2023
Oct. 31, 2022
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Fair Value $ 249,176 $ 181,378 $ 95,246
Long-term Investments, Fair Value 132,939 102,844 146,364
Amortized Cost 386,361 291,726 252,260
Unrealized Gains 155 41 0
Unrealized (Losses) (4,401) (7,545) (10,650)
Fair Value 382,115 284,222 241,610
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 251,479 183,023 103,305
Unrealized Gains 0 1 0
Unrealized (Losses) (2,303) (1,646) (8,059)
Fair Value 249,176 181,378 95,246
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 134,882 108,703 148,955
Unrealized Gains 155 40 0
Unrealized (Losses) (2,098) (5,899) (2,591)
Fair Value 132,939 102,844 146,364
Corporate Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 102,766 83,184 85,788
Unrealized Gains 0 0 0
Unrealized (Losses) (1,336) (947) (1,626)
Fair Value 101,430 82,237 84,162
Corporate Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 53,555 62,594 61,707
Unrealized Gains 4 22 0
Unrealized (Losses) (1,155) (3,319) (4,472)
Fair Value 52,404 59,297 57,235
Municipal and Pre-Refunded Municipal Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 48,115 48,141 58,417
Unrealized Gains 0 0 0
Unrealized (Losses) (727) (688) (910)
Fair Value 47,388 47,453 57,507
Municipal and Pre-Refunded Municipal Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 10,224 23,437 28,803
Unrealized Gains 3 5 0
Unrealized (Losses) (136) (1,154) (1,801)
Fair Value 10,091 22,288 27,002
Commercial Paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 20,976 21,636  
Unrealized Gains 0 0  
Unrealized (Losses) 0 0  
Fair Value 20,976 21,636  
US Treasury Securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 13,157 23,561 4,750
Unrealized Gains 0 1 0
Unrealized (Losses) (7) (10) (55)
Fair Value 13,150 23,552 4,695
US Treasury Securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 7,398    
Unrealized Gains 1    
Unrealized (Losses) (71)    
Fair Value 7,328    
Federal Government Agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 66,216 6,501  
Unrealized Gains 0 0  
Unrealized (Losses) (233) (1)  
Fair Value 65,983 6,500  
Federal Government Agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 49,203 9,021  
Unrealized Gains 13  
Unrealized (Losses) (388) (2)  
Fair Value 48,815 9,032  
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 13,252 13,402 12,546
Unrealized Gains 147 0 0
Unrealized (Losses) (348) (1,424) (1,786)
Fair Value 13,051 11,978 10,760
Certificates of Deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 249    
Unrealized Gains 0    
Unrealized (Losses) 0    
Fair Value 249    
Certificates of Deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,250 249 249
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0
Fair Value $ 1,250 $ 249 $ 249