v3.26.1
Marketable Securities - Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Jul. 31, 2026
Jan. 31, 2026
Jul. 31, 2025
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost $ 348,884 $ 786,644 $ 656,628
Unrealized Gains 163 2,486 1,231
Unrealized (Losses) (2,269) (548) (859)
Fair Value 346,778 788,582 657,000
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 117,390 326,124 290,849
Unrealized Gains 94 635 101
Unrealized (Losses) (113) (35) (286)
Fair Value 117,371 326,724 290,664
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 231,494 460,520 365,779
Unrealized Gains 69 1,851 1,130
Unrealized (Losses) (2,156) (513) (573)
Fair Value 229,407 461,858 366,336
Corporate bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 80,956 232,594 190,228
Unrealized Gains 52 403 59
Unrealized (Losses) (101) (28) (244)
Fair Value 80,907 232,969 190,043
Corporate bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 133,820 330,319 216,635
Unrealized Gains 26 921 469
Unrealized (Losses) (1,246) (436) (336)
Fair Value 132,600 330,804 216,768
US Treasury securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 17,486 38,288 12,724
Unrealized Gains 41 174 19
Unrealized (Losses) 0 (2) (2)
Fair Value 17,527 38,460 12,741
US Treasury securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 51,572 80,872 84,454
Unrealized Gains 23 520 351
Unrealized (Losses) (413) (20) (26)
Fair Value 51,182 81,372 84,779
Federal government agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,246 17,454 30,609
Unrealized Gains 0 32 11
Unrealized (Losses) (5) (2) (7)
Fair Value 2,241 17,484 30,613
Federal government agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 20,298 23,723 39,635
Unrealized Gains 0 10 3
Unrealized (Losses) (244) (55) (172)
Fair Value 20,054 23,678 39,466
Municipal and pre-refunded municipal bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 7,594 27,964 48,111
Unrealized Gains 1 26 12
Unrealized (Losses) (7) (3) (33)
Fair Value 7,588 27,987 48,090
Municipal and pre-refunded municipal bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 875 3,393 4,940
Unrealized Gains 0 17 10
Unrealized (Losses) (6) (1) (3)
Fair Value 869 3,409 4,947
Certificates of deposit | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 249 1,000 1,249
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 249 1,000 1,249
Certificates of deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 249    
Unrealized Gains 0    
Unrealized (Losses) 0    
Fair Value 249    
Commercial paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 8,859 8,824 7,928
Unrealized Gains 0 0 0
Unrealized (Losses) 0 0 0
Fair Value 8,859 8,824 7,928
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 24,680 22,213 20,115
Unrealized Gains 20 383 297
Unrealized (Losses) (247) (1) (36)
Fair Value $ 24,453 $ 22,595 $ 20,376