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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, 2024
Jan. 31, 2024
Oct. 31, 2023
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Fair Value $ 340,445 $ 286,744 $ 249,176
Long-term Investments, Fair Value 240,237 314,152 132,939
Amortized Cost 578,837 600,636 386,361
Unrealized Gains 2,836 2,323 155
Unrealized (Losses) (991) (2,063) (4,401)
Fair Value 580,682 600,896 382,115
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 340,396 312,536 251,479
Unrealized Gains 292 2,252
Unrealized (Losses) (243) (636) (2,303)
Fair Value 340,445 314,152 249,176
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 238,441 288,100 134,882
Unrealized Gains 2,544 71 155
Unrealized (Losses) (748) (1,427) (2,098)
Fair Value 240,237 286,744 132,939
Corporate Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 178,736 123,418 102,766
Unrealized Gains 151 27
Unrealized (Losses) (187) (883) (1,336)
Fair Value 178,700 122,562 101,430
Corporate Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 110,302 147,924 53,555
Unrealized Gains 266 441 4
Unrealized (Losses) (398) (388) (1,155)
Fair Value 110,170 147,977 52,404
Municipal and Pre-Refunded Municipal Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 64,129 47,915 48,115
Unrealized Gains 70 9
Unrealized (Losses) (33) (414) (727)
Fair Value 64,166 47,510 47,388
Municipal and Pre-Refunded Municipal Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 16,778 39,243 10,224
Unrealized Gains 30 160 3
Unrealized (Losses) (12) (35) (136)
Fair Value 16,796 39,368 10,091
Commercial Paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,943 10,557 20,976
Unrealized Gains 0
Unrealized (Losses) 0
Fair Value 2,943 10,557 20,976
US Treasury Securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,491 27,231 13,157
Unrealized Gains 0
Unrealized (Losses) (3) (36) (7)
Fair Value 1,488 27,195 13,150
US Treasury Securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 59,507 34,604 7,398
Unrealized Gains 197 169 1
Unrealized (Losses) (51) (26) (71)
Fair Value 59,653 34,747 7,328
Federal Government Agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 72,598 68,730 66,216
Unrealized Gains 71 35
Unrealized (Losses) (20) (94) (233)
Fair Value 72,649 68,671 65,983
Federal Government Agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 35,098 65,698 49,203
Unrealized Gains 16 138
Unrealized (Losses) (285) (94) (388)
Fair Value 34,829 65,742 48,815
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 15,756 13,817 13,252
Unrealized Gains 2,035 1,344 147
Unrealized (Losses) (2) (93) (348)
Fair Value 17,789 15,068 13,051
Certificates of Deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 20,499 10,249 249
Unrealized Gains 0
Unrealized (Losses) 0
Fair Value 20,499 10,249 249
Certificates of Deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,000 11,250 1,250
Unrealized Gains 0
Unrealized (Losses) 0
Fair Value $ 1,000 $ 11,250 $ 1,250