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Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities (Detail) - USD ($)
$ in Thousands
Oct. 31, 2022
Jan. 31, 2022
Oct. 31, 2021
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Amortized Cost $ 148,955 $ 239,929 $ 188,510
Short-term Investments, Unrealized Gains   2 12
Short-term Investments, Unrealized (Losses) 2,591 (511) 147
Short-term Investments, Fair Value 146,364 239,420 188,375
Long-term Investments, Amortized Cost 103,305 227,603 270,726
Long-term Investments, Unrealized Gains   1 551
Long-term Investments, Unrealized (Losses) 8,059 (4,047) 1,497
Long-term Investments, Fair Value 95,246 223,557 269,780
Amortized Cost 252,260 467,532 459,236
Unrealized Gains   3 563
Unrealized (Losses) (10,650) (4,558) (1,644)
Fair Value 241,610 462,977 458,155
Corporate Bonds      
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Amortized Cost 85,788 85,062 53,744
Short-term Investments, Unrealized Gains   1 3
Short-term Investments, Unrealized (Losses) (1,626) (200) 71
Short-term Investments, Fair Value 84,162 84,863 53,676
Long-term Investments, Amortized Cost 61,707 148,830 174,884
Long-term Investments, Unrealized Gains     1
Long-term Investments, Unrealized (Losses) 4,472 (2,478) 1,125
Long-term Investments, Fair Value 57,235 146,352 173,760
Municipal and Pre-Refunded Municipal Bonds      
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Amortized Cost 58,417 128,984 114,818
Short-term Investments, Unrealized Gains   1 9
Short-term Investments, Unrealized (Losses) (910) (273) 73
Short-term Investments, Fair Value 57,507 128,712 114,754
Long-term Investments, Amortized Cost 28,803 60,533 78,955
Long-term Investments, Unrealized Gains   1 8
Long-term Investments, Unrealized (Losses) (1,801) (912) 362
Long-term Investments, Fair Value 27,002 59,622 78,601
US Treasury Securities      
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Amortized Cost 4,750 14,999 16,849
Short-term Investments, Unrealized (Losses) (55) (38) 3
Short-term Investments, Fair Value 4,695 14,961 16,846
Long-term Investments, Amortized Cost   5,222 4,748
Long-term Investments, Unrealized (Losses)   (46) 7
Long-term Investments, Fair Value   5,176 4,741
Commercial Paper      
Schedule of Available-for-sale Securities [Line Items]      
Short-term Investments, Amortized Cost   10,884 3,099
Short-term Investments, Fair Value   10,884 3,099
Mutual Funds, Held in Rabbi Trust      
Schedule of Available-for-sale Securities [Line Items]      
Long-term Investments, Amortized Cost 12,546 12,419 11,540
Long-term Investments, Unrealized Gains     542
Long-term Investments, Unrealized (Losses) (1,786) (606) 1
Long-term Investments, Fair Value 10,760 11,813 12,081
Federal Government Agencies      
Schedule of Available-for-sale Securities [Line Items]      
Long-term Investments, Amortized Cost   350 350
Long-term Investments, Unrealized (Losses)   (5) 2
Long-term Investments, Fair Value   345 348
Certificates of Deposit      
Schedule of Available-for-sale Securities [Line Items]      
Long-term Investments, Amortized Cost 249 249 249
Long-term Investments, Fair Value $ 249 $ 249 $ 249