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Marketable Securities - Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Jan. 31, 2024
Jan. 31, 2023
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 600,636 $ 291,726
Unrealized Gains 2,323 41
Unrealized (Losses) (2,063) (7,545)
Fair Value 600,896 284,222
Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 312,536 108,703
Unrealized Gains 2,252 40
Unrealized (Losses) (636) (5,899)
Fair Value 314,152 102,844
Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 288,100 183,023
Unrealized Gains 71 1
Unrealized (Losses) (1,427) (1,646)
Fair Value 286,744 181,378
Municipal And Pre-Refunded Municipal Bonds | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 39,243 23,437
Unrealized Gains 160 5
Unrealized (Losses) (35) (1,154)
Fair Value 39,368 22,288
Municipal And Pre-Refunded Municipal Bonds | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 47,915 48,141
Unrealized Gains 9 0
Unrealized (Losses) (414) (688)
Fair Value 47,510 47,453
Corporate Bonds | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 147,924 62,594
Unrealized Gains 441 22
Unrealized (Losses) (388) (3,319)
Fair Value 147,977 59,297
Corporate Bonds | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 123,418 83,184
Unrealized Gains 27 0
Unrealized (Losses) (883) (947)
Fair Value 122,562 82,237
US Treasury Securities | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 34,604  
Unrealized Gains 169  
Unrealized (Losses) (26)  
Fair Value 34,747  
US Treasury Securities | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 27,231 23,561
Unrealized Gains 0 1
Unrealized (Losses) (36) (10)
Fair Value 27,195 23,552
Commercial Paper | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,557 21,636
Unrealized Gains 0 0
Unrealized (Losses) 0 0
Fair Value 10,557 21,636
Mutual Funds, Held in Rabbi Trust | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 13,817 13,402
Unrealized Gains 1,344 0
Unrealized (Losses) (93) (1,424)
Fair Value 15,068 11,978
Federal Government Agencies | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 65,698 9,021
Unrealized Gains 138 13
Unrealized (Losses) (94) (2)
Fair Value 65,742 9,032
Federal Government Agencies | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 68,730 6,501
Unrealized Gains 35 0
Unrealized (Losses) (94) (1)
Fair Value 68,671 6,500
Certificates of Deposit | Long-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 11,250 249
Unrealized Gains 0 0
Unrealized (Losses) 0 0
Fair Value 11,250 $ 249
Certificates of Deposit | Short-term Investments    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 10,249  
Unrealized Gains 0  
Unrealized (Losses) 0  
Fair Value $ 10,249