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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, 2023
Jan. 31, 2023
Jul. 31, 2022
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Fair Value $ 250,832 $ 181,378 $ 160,020
Long-term Investments, Fair Value 122,356 102,844 152,528
Amortized Cost 377,057 291,726 321,631
Unrealized Gains 1,028 41 0
Unrealized (Losses) (4,897) (7,545) (9,083)
Fair Value 373,188 284,222 312,548
Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 252,919 183,023 159,712
Unrealized Gains 1 1 0
Unrealized (Losses) (2,088) (1,646) (7,184)
Fair Value 250,832 181,378 152,528
Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 124,138 108,703 161,919
Unrealized Gains 1,027 40 0
Unrealized (Losses) (2,809) (5,899) (1,899)
Fair Value 122,356 102,844 160,020
Corporate Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 96,902 83,184 76,652
Unrealized Gains 1
Unrealized (Losses) (1,239) (947) (1,211)
Fair Value 95,664 82,237 75,441
Corporate Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 47,835 62,594 96,086
Unrealized Gains 22
Unrealized (Losses) (1,745) (3,319) (4,160)
Fair Value 46,090 59,297 91,926
Municipal and Pre-Refunded Municipal Bonds | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 48,350 48,141 75,518
Unrealized Gains
Unrealized (Losses) (670) (688) (595)
Fair Value 47,680 47,453 74,923
Municipal and Pre-Refunded Municipal Bonds | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 13,980 23,437 47,437
Unrealized Gains 5
Unrealized (Losses) (469) (1,154) (1,858)
Fair Value 13,511 22,288 45,579
Commercial Paper | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 41,719 21,636  
Unrealized Gains  
Unrealized (Losses)  
Fair Value 41,719 21,636  
US Treasury Securities | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 18,661 23,561 9,749
Unrealized Gains 1
Unrealized (Losses) (16) (10) (93)
Fair Value 18,645 23,552 9,656
US Treasury Securities | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 2,969   3,229
Unrealized Gains  
Unrealized (Losses) (61)   (129)
Fair Value 2,908   3,100
Federal Government Agencies | Short-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 47,287 6,501  
Unrealized Gains  
Unrealized (Losses) (163) (1)  
Fair Value 47,124 6,500  
Federal Government Agencies | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 44,914 9,021 350
Unrealized Gains 13
Unrealized (Losses) (464) (2) (12)
Fair Value 44,450 9,032 338
Mutual Funds, Held in Rabbi Trust | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 12,941 13,402 12,361
Unrealized Gains 1,027
Unrealized (Losses) (70) (1,424) (1,025)
Fair Value 13,898 11,978 11,336
Certificates of Deposit | Long-term Investments      
Schedule of Available-for-sale Securities [Line Items]      
Amortized Cost 1,499 249 249
Unrealized Gains
Unrealized (Losses)
Fair Value $ 1,499 $ 249 $ 249