v3.26.1
Marketable Securities - Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Apr. 30, 2026
Jan. 31, 2026
Apr. 30, 2025
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost $ 348,632 $ 786,644 $ 650,489
Unrealized Gains 2,138 2,486 2,227
Unrealized (Losses) (1,321) (548) (1,194)
Fair Value 349,449 788,582 651,522
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 111,871 326,124 285,605
Unrealized Gains 180 635 167
Unrealized (Losses) (73) (35) (187)
Fair Value 111,978 326,724 285,585
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 236,761 460,520 364,884
Unrealized Gains 1,958 1,851 2,060
Unrealized (Losses) (1,248) (513) (1,007)
Fair Value 237,471 461,858 365,937
Corporate bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 66,736 232,594 181,973
Unrealized Gains 95 403 102
Unrealized (Losses) (68) (28) (170)
Fair Value 66,763 232,969 181,905
Corporate bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 141,847 330,319 203,858
Unrealized Gains 116 921 915
Unrealized (Losses) (926) (436) (108)
Fair Value 141,037 330,804 204,665
US Treasury securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 13,465 38,288 3,952
Unrealized Gains 74 174 0
Unrealized (Losses) 0 (2) (3)
Fair Value 13,539 38,460 3,949
US Treasury securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 53,050 80,872 87,179
Unrealized Gains 148 520 989
Unrealized (Losses) (183) (20) 0
Fair Value 53,015 81,372 88,168
Federal government agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,213 23,723 38,187
Unrealized Gains 1 10 29
Unrealized (Losses) (3) (55) (4)
Fair Value 2,211 23,678 38,212
Federal government agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 16,608 17,454 46,308
Unrealized Gains 0 32 44
Unrealized (Losses) (134) (2) (90)
Fair Value 16,474 17,484 46,262
Municipal and pre-refunded municipal bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 21,647 27,964 43,152
Unrealized Gains 10 26 36
Unrealized (Losses) (2) (3) (10)
Fair Value 21,655 27,987 43,178
Municipal and pre-refunded municipal bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,761 3,393 6,775
Unrealized Gains 3 17 37
Unrealized (Losses) (4) (1) (2)
Fair Value 1,760 3,409 6,810
Certificates of deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost     10,499
Unrealized Gains     0
Unrealized (Losses)     0
Fair Value     10,499
Certificates of deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 249 1,000 1,000
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 249 1,000 1,000
Commercial paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 7,810 8,824 7,842
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 7,810 8,824 7,842
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 23,246 22,213 19,764
Unrealized Gains 1,691 383 75
Unrealized (Losses) (1) (1) (807)
Fair Value $ 24,936 $ 22,595 $ 19,032