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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, 2025
Jan. 31, 2025
Oct. 31, 2024
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost $ 654,748 $ 728,147 $ 578,837
Unrealized Gains 2,502 3,049 2,836
Unrealized (Losses) (274) (1,039) (991)
Fair Value 656,976 730,157 580,682
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 304,636 319,855 340,396
Unrealized Gains 536 228 292
Unrealized (Losses) (39) (134) (243)
Fair Value 305,133 319,949 340,445
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 350,112 408,292 238,441
Unrealized Gains 1,966 2,821 2,544
Unrealized (Losses) (235) (905) (748)
Fair Value 351,843 410,208 240,237
Corporate Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 233,479 186,732 178,736
Unrealized Gains 386 103 151
Unrealized (Losses) (36) (114) (187)
Fair Value 233,829 186,721 178,700
Corporate Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 219,737 233,418 110,302
Unrealized Gains 980 298 266
Unrealized (Losses) (172) (500) (398)
Fair Value 220,545 233,216 110,170
US Treasury Securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 18,768 5,415 1,491
Unrealized Gains 81 0 0
Unrealized (Losses) 0 (5) (3)
Fair Value 18,849 5,410 1,488
US Treasury Securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 75,430 92,852 59,507
Unrealized Gains 661 226 197
Unrealized (Losses) 0 (90) (51)
Fair Value 76,091 92,988 59,653
Federal Government Agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 14,735 53,663 72,598
Unrealized Gains 31 55 71
Unrealized (Losses) (2) (7) (20)
Fair Value 14,764 53,711 72,649
Federal Government Agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 29,602 50,579 35,098
Unrealized Gains 15 16 16
Unrealized (Losses) (51) (292) (285)
Fair Value 29,566 50,303 34,829
Municipal and Pre-Refunded Municipal Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 33,658 53,772 64,129
Unrealized Gains 38 70 70
Unrealized (Losses) (1) (8) (33)
Fair Value 33,695 53,834 64,166
Municipal and Pre-Refunded Municipal Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 3,591 14,770 16,778
Unrealized Gains 19 35 30
Unrealized (Losses) (3) (8) (12)
Fair Value 3,607 14,797 16,796
Certificates of Deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,000 10,499 20,499
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 1,000 10,499 20,499
Certificates of Deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost   1,000 1,000
Unrealized Gains   0 0
Unrealized (Losses)   0 0
Fair Value   1,000 1,000
Commercial Paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,996 9,774 2,943
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 2,996 9,774 2,943
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 21,752 15,673 15,756
Unrealized Gains 291 2,246 2,035
Unrealized (Losses) (9) (15) (2)
Fair Value $ 22,034 $ 17,904 $ 17,789