v3.26.1
Fair Value - Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Jan. 31, 2026
Jan. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis $ 788,582 $ 730,157
Fair Value, Measurements, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 788,582 730,157
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 22,595 17,904
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 765,987 712,253
Fair Value, Measurements, Recurring | Corporate Bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 563,773 419,937
Fair Value, Measurements, Recurring | Corporate Bonds | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 563,773 419,937
Fair Value, Measurements, Recurring | US Treasury Securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 119,832 98,398
Fair Value, Measurements, Recurring | US Treasury Securities | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 119,832 98,398
Fair Value, Measurements, Recurring | Federal Government Agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 41,162 104,014
Fair Value, Measurements, Recurring | Federal Government Agencies | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 41,162 104,014
Fair Value, Measurements, Recurring | Municipal And Pre-Refunded Municipal Bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 31,396 68,631
Fair Value, Measurements, Recurring | Municipal And Pre-Refunded Municipal Bonds | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 31,396 68,631
Fair Value, Measurements, Recurring | Mutual Funds, Held in Rabbi Trust    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 22,595 17,904
Fair Value, Measurements, Recurring | Mutual Funds, Held in Rabbi Trust | Fair Value, Inputs, Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 22,595 17,904
Fair Value, Measurements, Recurring | Commercial Paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 8,824 9,774
Fair Value, Measurements, Recurring | Commercial Paper | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 8,824 9,774
Fair Value, Measurements, Recurring | Certificates of Deposit    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis 1,000 11,499
Fair Value, Measurements, Recurring | Certificates of Deposit | Fair Value, Inputs, Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial assets accounted for at fair value on a recurring basis $ 1,000 $ 11,499