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Marketable Securities - Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Jul. 31, 2024
Jan. 31, 2024
Jul. 31, 2023
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Fair Value $ 352,360 $ 286,744 $ 250,832
Long-term Investments, Fair Value 209,469 314,152 122,356
Amortized Cost 560,836 600,636 377,057
Unrealized Gains 2,105 2,323 1,028
Unrealized (Losses) (1,112) (2,063) (4,897)
Fair Value 561,829 600,896 373,188
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 353,116 288,100 252,919
Unrealized Gains 50 71 1
Unrealized (Losses) (806) (1,427) (2,088)
Fair Value 352,360 286,744 250,832
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 207,720 312,536 124,138
Unrealized Gains 2,055 2,252 1,027
Unrealized (Losses) (306) (636) (2,809)
Fair Value 209,469 314,152 122,356
Corporate Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 179,538 123,418 96,902
Unrealized Gains 26 27 1
Unrealized (Losses) (567) (883) (1,239)
Fair Value 178,997 122,562 95,664
Corporate Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 79,873 147,924 47,835
Unrealized Gains 147 441 0
Unrealized (Losses) (87) (388) (1,745)
Fair Value 79,933 147,977 46,090
Municipal and Pre-Refunded Municipal Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 47,174 47,915 48,350
Unrealized Gains 17 9 0
Unrealized (Losses) (65) (414) (670)
Fair Value 47,126 47,510 47,680
Municipal and Pre-Refunded Municipal Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 25,250 39,243 13,980
Unrealized Gains 19 160 0
Unrealized (Losses) (69) (35) (469)
Fair Value 25,200 39,368 13,511
Commercial Paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,905 10,557 41,719
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 2,905 10,557 41,719
US Treasury Securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 29,150 27,231 18,661
Unrealized Gains 0 0 0
Unrealized (Losses) (59) (36) (16)
Fair Value 29,091 27,195 18,645
US Treasury Securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 49,951 34,604 2,969
Unrealized Gains 200 169 0
Unrealized (Losses) (45) (26) (61)
Fair Value 50,106 34,747 2,908
Federal Government Agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 73,850 68,730 47,287
Unrealized Gains 7 35 0
Unrealized (Losses) (115) (94) (163)
Fair Value 73,742 68,671 47,124
Federal Government Agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 35,635 65,698 44,914
Unrealized Gains 7 138 0
Unrealized (Losses) (105) (94) (464)
Fair Value 35,537 65,742 44,450
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 16,011 13,817 12,941
Unrealized Gains 1,682 1,344 1,027
Unrealized (Losses) 0 (93) (70)
Fair Value 17,693 15,068 13,898
Certificates of Deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 20,499 10,249  
Unrealized Gains 0 0  
Unrealized (Losses) 0 0  
Fair Value 20,499 10,249  
Certificates of Deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,000 11,250 1,499
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value $ 1,000 $ 11,250 $ 1,499